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Guide to Physics IIT JEE

Ravi Raj Dudeja

Chapter 22

Thermal and Chemical Effects of Current - all with Video Answers

Educators

Chapter Questions

02:29

Problem 1

Faraday constant
(a) depends on the amount of the electrolyte
(b) depends on the current in the electrolyte
(c) is a universal constant
(d) depends on the amount of charge passed through the electrolyte.

Himanshu Kushwaha
Himanshu Kushwaha
Numerade Educator
00:54

Problem 2

An electrolysis experiment is stopped and the battery terminals are reversed.
(a) The electrolysis will stop.
(b) The rate of liberation of material at the electrodes will increase.
(c) The rate of liberation of material will remain the same.
(d) Heat will be produced at a greater rate.

Mishal Gul
Mishal Gul
Numerade Educator
01:48

Problem 3

Consider the following two statements.
(A) Free electron density is different in different metals.
(B) Free electron density in a metal depends on temperature.
Seebeck effect is caused
(a) due to both $A$ and $B$
(b) due to $A$ but not due to $B$
(c) due to $B$ but not due to $A$
(d) neither due to $A$ nor due to $B$.

Sachin Rao
Sachin Rao
Numerade Educator
02:08

Problem 4

The electrochemical equivalent of a material depends on
(a) the nature of the material
(b) the current through the electrolyte containing the material
(c) the amount of charge passed through the electrolyte
(d) the amount of this material present in the electrolyte.

Shahina -
Shahina -
Numerade Educator
03:26

Problem 5

According to Joule's law, if the potential difference across a conductor of resistivity $\rho$ remains constant, then the heat produced in the conductor is proportional to
(a) $\frac{1}{\rho}$
(b) $\frac{1}{\sqrt{\rho}}$
(c) $\rho^2$
(d) $\rho$

Prem Bijarniya
Prem Bijarniya
Numerade Educator
01:36

Problem 6

Two electric bulbs, each designed to operate with a power of $500 \mathrm{~W}$ in a $220 \mathrm{I}$ line, are connected in series with a $110 \mathrm{~V}$ 'line. The power consumed in each bulb is
(a) $125 \mathrm{~W}$
(b) $93.75 \mathrm{~W}$
(c) $62.5 \mathrm{~W}$
(d) $31.25 \mathrm{~W}$

Nishant Kumar
Nishant Kumar
Numerade Educator
01:57

Problem 7

A constant voltage is applied between the two ends of a uniform metallic wire, some heat is developed in it. If both the length and the radius of the wire are halved, the heat developed in the same duration will become
(a) four times
(b) one fourth
(c) twice
(d) half

Satpal Satpal
Satpal Satpal
Numerade Educator
01:33

Problem 8

A house wiring, supplied with a $220 \mathrm{~V}$ "supply line, is protected by a 9 amp. fuse. The maximum number of 60 $W$ bulbs in parallel that can be turned on is
(a) 44
(b) 33
(c) 22
(d) 11

Varsha Aggarwal
Varsha Aggarwal
Numerade Educator
01:17

Problem 9

A uniform wire connected across a supply produces heat $\mathrm{H}$ per second. If the wire is cut into $\mathrm{n}$ equal parts and all the parts are connected in parallel across the same supply, the heat produced per second will be
(a) $\frac{H}{n^2}$
(b) $n^2 H$
(c) $n \mathrm{H}$
(d) $\frac{H}{n}$

Varsha Aggarwal
Varsha Aggarwal
Numerade Educator
03:42

Problem 10

An $800 \mathrm{~W}, 220 \mathrm{I}$ 'kettle and three $100 \mathrm{~W}, 220 \mathrm{I}$ 'bulbs are connected in parallel across a $220 \mathrm{I}$ 'source. The current drawn from the source is
(a) $6.9 \mathrm{~A}$
(b) $5.5 \mathrm{~A}$
(c) $5.0 \mathrm{~A}$
(d) $0.15 \mathrm{~A}$

Rachel B.
Rachel B.
Numerade Educator
01:25

Problem 11

Two electric bulbs, one of $200 \mathrm{I}^*-40 \mathrm{~W}$ and other of $200 \mathrm{~V}^*-100 \mathrm{~W}$ are connected in house wiring circuit.
(a) The resistance of $100 \mathrm{~W}$ bulb is more than that of $40 \mathrm{~W}$ bulb.
(b) The resistance of $40 \mathrm{~W}$ bulb is more than that of $100 \mathrm{~W}$ bulb
(c) The resistances of bulbs are equal.
(d) Both the bulbs carry equal currents.

Saman Zulfiqar
Saman Zulfiqar
Numerade Educator
01:25

Problem 12

In Q. 16 , if the bulbs are connected in series with a 200 I'line, then
(a) the potential drop across two bulbs is the same
(b) the potential drop across $40 \mathrm{~W}$ bulb is greater than that across $100 \mathrm{~W}$ bulb
(c) the potential drop across $100 \mathrm{~W}$ bulb is greater than that across $40 \mathrm{~W}$ bulb
(d) none of these

Saman Zulfiqar
Saman Zulfiqar
Numerade Educator
01:28

Problem 13

Two heater coils separately take $10 \mathrm{~min}$ and $5 \mathrm{~min}$ to boil a certain amount of water. If both the coils are connected in series, the time taken will be
(a) $2.5 \mathrm{~min}$
(b) $3.33 \mathrm{~min}$
(c) $75 \mathrm{~min}$
(d) $15 \mathrm{~min}$

Prem Bijarniya
Prem Bijarniya
Numerade Educator
02:36

Problem 14

In Q. 13, if the coils are connected in parallel the time taken will be
(a) $6.66 \mathrm{~min}$
(b) $7.5 \mathrm{~min}$
(c) $3.33 \mathrm{~min}$
(d) $2.5 \mathrm{~min}$

Satpal Satpal
Satpal Satpal
Numerade Educator
01:06

Problem 15

Two electrical appliances are connected in parallel to a constant voltage supply. If the current in one appliance is $1 \%$ less than that in the second appliance, then the power of the first appliance will be less by
(a) $5 \%$
(b) $4 \%$
(c) $2 \%$
(d) $1 \%$

Satpal Satpal
Satpal Satpal
Numerade Educator
01:44

Problem 16

The parameter irrelevant for an electric fuse wire is
(a) its radius
(b) its specific resistance
(c) current flowing through it
(d) its length

Sachin Rao
Sachin Rao
Numerade Educator
02:23

Problem 17

In the circuit shown, the heat produced in $5 \Omega$ resistor is $10 \mathrm{calorie} / \mathrm{sec}$. The heat produced $/ \mathrm{sec}$ in $4 \Omega$ resistor will be
(Figure can't copy)
(a) $1 \mathrm{cal}$
(b) $2 \mathrm{cal}$
(c) $3 \mathrm{cal}$
(d) $4 \mathrm{cal}$

Mahipal Kumawat
Mahipal Kumawat
Numerade Educator
01:01

Problem 18

The neutral temperature of a thermocouple is $275^{\circ} \mathrm{C}$ and the temperature of inversion is $600^{\circ} \mathrm{C}$. The temperature of the cold junction is
(a) $50^{\circ} \mathrm{C}$
(b) $25^{\circ} \mathrm{C}$
(c) $-25^{\circ} \mathrm{C}$
(d) $-50^{\circ} \mathrm{C}$

Narayan Hari
Narayan Hari
Numerade Educator
00:56

Problem 19

Two cells, each of emf $2 \mathrm{I}$ and internal resistance $1 \Omega$ are given. The maximum heat that can be produced in a resistance of $0.5 \Omega$ with the help of given two cells is
(a) $4.2 \mathrm{~W}$
(b) $2.9 \mathrm{~W}$
(c) $2.0 \mathrm{~W}$
(d) $1 \mathrm{~W}$

Varsha Aggarwal
Varsha Aggarwal
Numerade Educator
01:52

Problem 20

The thermo-emf of a copper-constant couple is $40 \mu \mathrm{I}^{\circ}$ per degree. The smallest temperature difference that can be detected with this couple and a galvanometer of $100 \Omega$ resistance capable of measuring the minimum current of $1 \mu \mathrm{A}$ is
(a) $2.5^{\circ} \mathrm{C}$
(b) $2^{\circ} \mathrm{C}$
(c) $1.5^{\circ} \mathrm{C}$
(d) $1^{\circ} \mathrm{C}$

Dheeraj Sharma
Dheeraj Sharma
Numerade Educator
01:34

Problem 21

Two electric bulbs, each designed to operate with a power of $500 \mathrm{~W}$ in $220 \mathrm{~V}$ 'line, are connected in series in a $110 \mathrm{~J}$ 'line. The power generated by each bulb will be
(a) $11 \mathrm{~W}$
(b) $312.5 \mathrm{~W}$
(c) $22 \mathrm{~W}$
(d) $31.25 \mathrm{~W}$

Mahipal Kumawat
Mahipal Kumawat
Numerade Educator
02:55

Problem 22

A resistance coil of $60 \Omega$ is immersed in $42 \mathrm{~kg}$ of water What is the rise in temperature of water per minute if a steady current of $7 \mathrm{~A}$ is made to flow through the coil?
(a) $10.19^{\circ} \mathrm{C}$
(b) $9.15^{\circ} \mathrm{C}$
(c) $1.0^{\circ} \mathrm{C}$
(d) $0.5^{\circ} \mathrm{C}$

Mahendra K
Mahendra K
Numerade Educator
03:01

Problem 23

In the circuit shown below, the power supplied by the battery is
(Figure can't copy)
(a) $5 W$
(b) $25 \mathrm{~W}$
(c) $10 \mathrm{~W}$
(d) $25 \mathrm{~W}$

Rachel B.
Rachel B.
Numerade Educator
01:48

Problem 24

When different parts of a metal are kept at different temperatures and current is passed through it, heat is either evolved or absorbed. This effect is called
(a) Thomson effect
(b) Seebeck effect
(c) Peltier effect
(d) none of these

Satpal Satpal
Satpal Satpal
Numerade Educator
01:37

Problem 25

In a metal with positive Thomson coefficient, current is passed from the lower temperature to higher temperature side, then
(a) heat will be evolved
(b) heat will be absorbed
(c) heat is neither absorbed nor evolved
(d) none of these

Prem Bijarniya
Prem Bijarniya
Numerade Educator
01:29

Problem 26

The emf in a thermoelectric circuit with one junction at 0 and the other at $t^{\circ} \mathrm{C}$ is given by $E=a t+b t^2$. The neutral temperature is
(a) $\frac{2 b}{a}$
(b) $\frac{a}{b}$
(c) $-\frac{a}{b}$
(d) $-\frac{a}{2 b}$

Dheeraj Sharma
Dheeraj Sharma
Numerade Educator
01:01

Problem 27

In a given thermocouple, the temperature of cold junction is $20^{\circ} \mathrm{C}$ while the neutral temperature is $270^{\circ} \mathrm{C}$. The temperature of inversion is
(a) $590^{\circ} \mathrm{C}$
(b) $520^{\circ} \mathrm{C}$
(c) $470^{\circ} \mathrm{C}$
(d) $420^{\circ} \mathrm{C}$

Narayan Hari
Narayan Hari
Numerade Educator
01:52

Problem 28

The thermo-emf of a thermocouple is $40 \mu \mathrm{V}$ 'per degree temperature difference. A galvanometer of $50 \Omega$ resistance capable of detecting current as low as $10 \mathrm{~A}$ is connected with one such thermocouple. The smallest temperature difference that can be detected by such a thermocouple is
(a) $17.5^{\circ} \mathrm{C}$
(b) $12.5^{\circ} \mathrm{C}$
(c) $8.5^{\circ} \mathrm{C}$
(d) $2.5^{\circ} \mathrm{C}$

Dheeraj Sharma
Dheeraj Sharma
Numerade Educator
01:15

Problem 29

Amount of energy absorbed or evolved when one ampere of current passes for one second through a metal kept at a temperature difference of $1^{\circ} \mathrm{C}$ is called
(a) Thermo-emf
(b) Thermoelectric power
(c) Thomson coefficient
(d) Peltier coefficient

Satpal Satpal
Satpal Satpal
Numerade Educator
02:11

Problem 30

Two electroplating cells, one of silver and another of aluminum are connected in series. The ratio of the number of silver atoms to that of aluminum atoms deposited during time $t$ will be
(a) $1: 9$
(b) $9: 1$
(c) $1: 3$
(d) $3: 1$

Satpal Satpal
Satpal Satpal
Numerade Educator
02:42

Problem 31

10 A current deposits $10.8 \mathrm{gm}$ silver in $900 \mathrm{~s}$. The mass of copper deposited by $9 \mathrm{~A}$ current in 1200 s will be
(a) $12.7 \mathrm{gm}$
(b) $10.8 \mathrm{gm}$
(c) $6.35 \mathrm{gm}$
(d) $3.8 \mathrm{gm}$

Saman Zulfiqar
Saman Zulfiqar
Numerade Educator
02:17

Problem 32

A silver and a zinc voltameters are connected in series. A current is passed through them for time $t$. If $W \mathrm{gm}$ zine is liberated, then the weight of silver deposited will be nearly
(a) $3.3 \mathrm{~W}$
(b) $2.4 \mathrm{~W}$
(c) $1.7 \mathrm{~W}$
(d) $1.1 \mathrm{~W}$

Satpal Satpal
Satpal Satpal
Numerade Educator
01:03

Problem 33

What is the approximate strength of current that will deposit $0.5 \mathrm{gm}$ of silver on a spoon in 7.5 minutes? (Given e.c.e. of silver $-0.001118 \mathrm{gmC}^{-1}$ )
(a) $1 \mathrm{~A}$
(b) $0.005 \mathrm{~A}$
(c) $0.5 \mathrm{~A}$
(d) $0.1 \mathrm{~A}$

Satpal Satpal
Satpal Satpal
Numerade Educator
02:42

Problem 34

1A of current flowing through a silver voltameter for 25 minutes deposits $1.5 \mathrm{gm}$ of silver. The e.c.e. of silver will be (in $\mathrm{gmC}^{-1}$ )
(a) 0.0001
(b) 0.001
(c) 0.01
(d) 0.1

Saman Zulfiqar
Saman Zulfiqar
Numerade Educator
02:01

Problem 35

An ammeter, suspected to give inaccurate reading, is connected in series with a silver voltameter. The ammeter indicates $0.54 \mathrm{~A}$. A steady current passed for one hour deposits $2.0124 \mathrm{gm}$ of silver. If the e.c.e. of silver is $1.118 \times 10^{-3} \mathrm{gmC}^{-1}$, then the error in ammeter reading is
(a) $+0.04 \mathrm{~A}$
(b) $+0.02 \mathrm{~A}$
(c) $-0.03 \mathrm{~A}$
(d) $-0.01 \mathrm{~A}$

Satpal Satpal
Satpal Satpal
Numerade Educator
01:55

Problem 36

Consider a thermocouple made of iron and constantan If the thermo emf's of iron and constantan against platinum are +800 and $-1700 \mu \mathrm{I}$ 'per $50^{\circ} \mathrm{C}$ difference of temperature, then the emf developed per ${ }^{\circ} \mathrm{C}$ difference of temperature between the junctions will be (in $\mu \mathrm{I}^7$ 7 ${ }^{\circ} \mathrm{C}$ )
(a) 200
(b) 150
(c) 100
(d) 50

Satpal Satpal
Satpal Satpal
Numerade Educator
01:32

Problem 37

A beam of $16 \mathrm{Mel}^{\prime}$ deutrons from a cyclotron falls on a copper block. The beam is equivalent to a current of $15 \mu \mathrm{A}$. At what rate do the deutrons strike the block?
(a) $9.4 \times 10^9$
(b) $9.4 \times 10^7$
(c) $9.4 \times 10^{11}$
(d) $9.4 \times 10^{13}$

Salamat Ali
Salamat Ali
Numerade Educator
01:34

Problem 38

An electric bulb is operating at $110 \mathrm{~V}$. Power consumed by it, if it is rated $220 \mathrm{I}^{\circ}-100 \mathrm{~W}$, will be
(a) $90 \mathrm{~W}$
(b) $75 \mathrm{~W}$
(c) $50 \mathrm{~W}$
(d) $25 \mathrm{~W}$

Mahipal Kumawat
Mahipal Kumawat
Numerade Educator
01:36

Problem 39

The same mass of copper is drawn into two wires $1 \mathrm{~mm}$ and $2 \mathrm{~mm}$ thick. Two wires are connected in series and current is passed through them. Heat produced in the wires is in the ratio
(a) $2: 1$
(b) $1: 16$
(c) $4: 1$
(d) $16: 1$

Satpal Satpal
Satpal Satpal
Numerade Educator
01:22

Problem 40

The two head lamps of a car are in parallel. Together they consume $48 \mathrm{~W}$ with the help of a $6 \mathrm{I}$ battery. The resistance of each bulb is
(a) $1.5 \Omega$
(b) $4.0 \Omega$
(c) $0.67 \Omega$
(d) $3.0 \Omega$

Varsha Aggarwal
Varsha Aggarwal
Numerade Educator
01:43

Problem 41

A coil of wire of resistance $50 \Omega$ is embedded in a block of ice. If a potential difference of $210 \mathrm{I}$ " is applied across the coil, the amount of ice melted per second will be
(a) $4.12 \mathrm{gm}$
(b) $4.12 \mathrm{~kg}$
(c) $3.68 \mathrm{~kg}$
(d) $2.625 \mathrm{gm}$

Satpal Satpal
Satpal Satpal
Numerade Educator
05:03

Problem 42

A steady potential difference of $1 \mathrm{GQV}$ produces heat at a constant rate in a resistor. The altemating voltage which will produce half the heating effect in the same resistor will be
(a) $100 \mathrm{~V}^{\circ}$
(b) $50 \mathrm{I}^{\circ}$
(c) $70.7 \mathrm{~V}^*$
(d) $141.4 \mathrm{I}^{\circ}$

Prem Bijarniya
Prem Bijarniya
Numerade Educator
02:08

Problem 43

Copper and silver voltameters are connected in series. If $0.8 \mathrm{gm}$ of copper is deposited in copper voltameter, then the amount of silver deposited in silver voltameter will be (Chemical equivalents of copper and silver are 32 and 108 respectively).
(a) $0.27 \mathrm{~kg}$
(b) $2.7 \mathrm{~kg}$
(c) $27 \mathrm{gm}$
(d) $2.7 \mathrm{gm}$

Mahipal Kumawat
Mahipal Kumawat
Numerade Educator
01:17

Problem 44

In a copper voltameter, the mass deposited in $30 \mathrm{~s}$ is $m$ gram. If the current time graph is as shown in the figure, the e.c.e. of copper, in gm/coul, will be
(Figure can't copy)
(a) $m$
(b) $\frac{m}{2}$
(c) $0.6 \mathrm{~m}$
(d) $0.1 \mathrm{~m}$

Amita Prajapat
Amita Prajapat
Numerade Educator
01:32

Problem 45

If a current of $2 \mathrm{~A}$ flowing for 1 hour liberates a certain amount of ions, then a current of $8 \mathrm{~A}$ flowing for the same time will liberate ions
(a) sixteen times
(b) six times
(c) eight times
(d) four times

Satpal Satpal
Satpal Satpal
Numerade Educator
01:02

Problem 46

If $1 \mathrm{~A}$ current is passed through $\mathrm{CuSO} 4$ solution for $10 \mathrm{~s}$, the number of copper atoms deposited at the cathode will approximately be
(a) $3.1 \times 10^{19}$
(b) $6.2 \times 10^{15}$
(c) $9.3 \times 10^{19}$
(d) $1.6 \times 10^{15}$

Narayan Hari
Narayan Hari
Numerade Educator
02:58

Problem 47

How much electricity should be passed through a water voltameter in order to release 22.4 litre of hydrogen at N.T.P.?
(a) 1 coul
(b) $22.4 \mathrm{coul}$
(c) 96500 coul
(d) $1,93,000 \mathrm{coul}$

Mahipal Kumawat
Mahipal Kumawat
Numerade Educator
01:16

Problem 48

If $N$ is the Avogadro number and $\mathrm{e}$ is the electronic charge then the Faraday constant $F$ is equal to
(a) $\mathrm{Ne}$
(b) $N^2 e$
(c) $\frac{\mathrm{N}}{\mathrm{e}}$
(d) $\frac{e}{N}$

Dr. Satish Ingale
Dr. Satish Ingale
Numerade Educator
02:21

Problem 49

A $3 \Omega$ resistor and a silver voltameter of resistance $2 \Omega$ are connected in series across a cell. How will the rate of deposition of silver be affected if a resistance of $2 \Omega$ is connected in parallel with the voltameter?
(a) It will decrease by $25 \%$
(b) It will increase by $25 \%$
(c) It will increase by $37.5 \%$
(d) It will decrease by $37.5 \%$

Mahipal Kumawat
Mahipal Kumawat
Numerade Educator
01:28

Problem 50

In an electroplating experiment, $m$ grams of silver are deposited when $4 \mathrm{~A}$ current flows for 2 minutes. The amount (in grams) of silver deposited by $6 \mathrm{~A}$ of current flowing for 40 s will be
(a) $2 m$
(b) $\frac{m}{4}$
(c) $\frac{m}{2}$
(d) $4 \mathrm{~m}$

Satpal Satpal
Satpal Satpal
Numerade Educator
01:34

Problem 51

E.C.E. of a substance is its mass liberated at an electrode by what amount of current in half a second
(a) $4 \mathrm{~A}$
(b) $3 A$
(c) $2 \mathrm{~A}$
(d) $1 \mathrm{~A}$

Satpal Satpal
Satpal Satpal
Numerade Educator
01:23

Problem 52

If $100 \mathrm{KWh}$ of energy is consumed at $33 \mathrm{~V}$ in a copper voltameter, the mass of copper liberated is (Given: e.c.e. of copper $=3.3 \times 10^{-7} \mathrm{~kg} / \mathrm{C}$ )
(a) $1.65 \mathrm{~kg}$
(b) $1.8 \mathrm{~kg}$
(c) $3.3 \mathrm{~kg}$
(d) $3.6 \mathrm{~kg}$

Satpal Satpal
Satpal Satpal
Numerade Educator
02:42

Problem 53

A current of $1.5 \mathrm{~A}$ flows through a copper voltameter. The thickness of copper deposited on the electrode surface of area $50 \mathrm{~cm}$ in 20 minutes will be (Density of copper $=9000 \mathrm{~kg} / \mathrm{m}^3$ and e.c.e, of copper $=0.00033$ $\mathrm{g} / \mathrm{C})$
(a) $2.6 \times 10^{-5} \mathrm{~m}$
(b) $26 \times 10^{-4} \mathrm{~m}$
(c) $1.3 \times 10^{-5} \mathrm{~m}$
(d) $1.3 \times 10^{-4} \mathrm{~m}$

Saman Zulfiqar
Saman Zulfiqar
Numerade Educator
01:01

Problem 54

A current of $16 \mathrm{~A}$ flows through molten $\mathrm{NaCl}$ for 10 minutes. The amount of metallic sodium that appears at the negative electrode would be (Faraday constant $=9.65 \times 10 \mathrm{C}$ )
(a) $11.5 \mathrm{gm}$
(b) $2.3 \mathrm{gm}$
(c) $1.15 \mathrm{gm}$
(d) $0.23 \mathrm{gm}$

Alkendra Singh
Alkendra Singh
Numerade Educator
01:43

Problem 55

For a given temperature difference, which of the following pairs will generate maximum thermo $\mathrm{emf}$ ?
(a) Lead-nickel
(b) Iron-copper
(c) Silver-gold
(d) Antimony-bismuth

Satpal Satpal
Satpal Satpal
Numerade Educator
01:25

Problem 56

A $500 \mathrm{~W}$ heating unit is designed to operate on a $115 \mathrm{~V}$ line. If the line voltage drops to $110 \mathrm{~V}$ line, the percentage drop in heat output will be
(a) $7.6 \%$
(b) $8.5 \%$
(c) $8.1 \%$
(d) $10.2 \%$

Salamat Ali
Salamat Ali
Numerade Educator
01:36

Problem 57

Which of the following statements is correct?
(a) Seebeck effect is irreversible.
(b) Thomson effect is localised at the junction.
(c) Joule heating effect is independent of the direction of flow of current in a conductor.
(d) Thomson effect is similar in origin to Peltier effect. They both are due to non-uniform distribution of electrons in a metal.

Satpal Satpal
Satpal Satpal
Numerade Educator
01:36

Problem 58

Which of the following statements is correct?
(a) Both Peltier and Joule effects are reversible.
(b) Both Peltier and Joule effects are irreversible.
(c) Joule effect is reversible whereas Peltier effect is irreversible.
(d) Joule effect is irreversible whereas Peltier effect is reversible.

Satpal Satpal
Satpal Satpal
Numerade Educator
01:21

Problem 59

A thermocouple is made from copper and iron. At the hot junction, the current
(a) flows from copper towards iron
(b) flows from iron towards copper
(c) flow decreases
(d) flow increases

Satpal Satpal
Satpal Satpal
Numerade Educator
01:38

Problem 60

The power of a heater is $500 \mathrm{~W}$ at $800^{\circ} \mathrm{C}$. What will be its power at $200^{\circ} \mathrm{C}$ it $\alpha=4 \times 10^{-4}$ per ${ }^{\circ} \mathrm{C}$ ?
(a) $611 \mathrm{~W}$
(b) $576 \mathrm{~W}$
(c) $672 \mathrm{~W}$
(d) $484 \mathrm{~W}$

Mahipal Kumawat
Mahipal Kumawat
Numerade Educator
03:15

Problem 61

A, B, C are three identical lamps connected as shown in the following figure. What changes occur in the brightness of the lamps when switch $\mathrm{S}$ is closed?
(Figure can't copy)
(a) Brightness of $\mathrm{A}$ increases but that of $\mathrm{B}$ decreases.
(b) Brightness of $A$ remains same but that of $B$ decreases.
(c) Brightness of $\mathrm{A}$ increases but that of $\mathrm{B}$ remains same.
(d) Brightness of both $\mathrm{A}$ and $\mathrm{B}$ decreases.

Sheh Lit Chang
Sheh Lit Chang
University of Washington
10:04

Problem 62

In the following figure all the bulbs connected are identical. The bulb that lights most brilliantly is
(Figure can't copy)
(a) only 1
(b) only 2
(c) 1 and 5
(d) 2 and 4

Ren Jie Tuieng
Ren Jie Tuieng
Numerade Educator
01:40

Problem 63

The rate of heating of $10 \mathrm{~A} \mathrm{AC}$ current is the same as the rate of heating of a DC current of
(a) $\frac{10}{\sqrt{2}} \mathrm{~A}$
(b) $10 \sqrt{2} \mathrm{~A}$
(c) $10 \mathrm{~A}$
(d) $5 \mathrm{~A}$

Prem Bijarniya
Prem Bijarniya
Numerade Educator
01:43

Problem 64

The resistance of a carbon filament at $0^{\circ} \mathrm{C}$ is $104 \Omega$. It is connected in series with an iron wire. The temperature coefficients of resistivity of carbon and iron are -0.0003 and 0.0052 per ${ }^{\circ} \mathrm{C}$ respectively. What must be the resistance of iron wire so that the combined resistance does not change with temperature ?
(a) $1.8 \Omega$
(b) $3.7 \Omega$
(c) $6.0 \Omega$
(d) $15 \Omega$

Satpal Satpal
Satpal Satpal
Numerade Educator
03:23

Problem 65

Two metallic wires of same material and same length have different diameters When connected in series across a battery, the heat produced in thinner wire is $Q_1$ and that in thicker one is $Q_2$. The correct relation is
(a) $Q_1=Q_2$
(b) $Q_1<Q_2$
(c) $Q_1>Q_2$
(d) will depend on the emf of the battery.

Nishant Kumar
Nishant Kumar
Numerade Educator
02:31

Problem 66

In the above problem, if the wires are connected in parallel, then
(a) $Q_1-Q_2$
(c) $Q_1>Q_2$
(b) $Q_1<Q_2$
(d) will depend on the emf of the battery.

Mahendra Kumar
Mahendra Kumar
Numerade Educator
01:05

Problem 67

The power dissipated in a conductor of resistivity $a$ is proportional to
(a) $\rho^2$
(b) $\rho$
(c) $\sqrt{\rho}$
(d) none of these

Mirza Aslam Beig
Mirza Aslam Beig
Numerade Educator
01:22

Problem 68

Charge carriers in a thermocouple are-
(a) $+v e$ ions
(b) -ve ions
(c) electrons
(d) protons

Subash Charan
Subash Charan
Numerade Educator
01:20

Problem 69

The emf of the battery in a thermocouple is doubled. The rate of heat generation at one of the junctions will
(a) remain unchanged
(b) become half
(c) become double
(d) become four times

Vishal Gupta
Vishal Gupta
Numerade Educator
01:46

Problem 70

The unit of Peltier coefficient is
(a) $\mathrm{JC}^{-1}$
(b) $\mathrm{JA}^{-1}$
(c) $\mathrm{JV}^{-1}$
(d) none of these

Amita Prajapat
Amita Prajapat
Numerade Educator
01:22

Problem 71

The unit of Thomson's coefficient is
(a) $\mathrm{JC}^{-4}$
(b) $\mathrm{JA}^{-1}$
(c) $\mathrm{JV}^{-1}$
(d) none of these

Rachel B.
Rachel B.
Numerade Educator
01:53

Problem 72

Masses of three wires are in the ratio $1: 3: 5$. Their lengths are in the ratio $5: 3: 1$. When connected in series with a battery the ratio of heats produced in them will be
(a) $125: 15: 1$
(b) $1: 15: 125$
(c) $5: 3: 1$
(d) $1: 3: 5$

Prem Bijarniya
Prem Bijarniya
Numerade Educator
02:09

Problem 73

In the above problem, if the wires are connected in parallel to the battery, then the amounts of heat produced will be
(a) $125: 15: 1$
(b) $1: 15: 125$
(c) $5: 3: 1$
(d) $1: 3: 5$

Prem Bijarniya
Prem Bijarniya
Numerade Educator
00:56

Problem 74

Two identical batteries, each of emf $2 \mathrm{~V}$ and intemal resistance $1 \Omega$, are available to produce heat in an extemal circuit. The maximum rate of production of heat in the external circuit will be
(a) $1 \mathrm{~W}$
(b) $8 \mathrm{~W}$
(c) $4 \mathrm{~W}$
(d) $2 \mathrm{~W}$

Varsha Aggarwal
Varsha Aggarwal
Numerade Educator
01:37

Problem 75

A heater boils I $\mathrm{kg}$ of water in lime $t_1$. Another heater boils it in lime $t_2$. If both are connected in series, the combination will boil same water in time
(a) $\frac{t_1+t_2}{2}$
(b) $\left(t_1+t_2\right)$
(c) $\frac{t_1 t_2}{t_1+t_2}$
(d) $\frac{t_1 t_2}{t_1-t_2}$

Hunza Gilgit
Hunza Gilgit
Numerade Educator
01:23

Problem 76

A tap supplies water at $22^{\circ} \mathrm{C}$. A man takes 1 litre per minute at $37^{\circ} \mathrm{C}$ from the geyser. The power of geyser is
(a) $2100 \mathrm{~W}$
(b) $1050 \mathrm{~W}$
(c) $1575 \mathrm{~W}$
(d) $525 \mathrm{~W}$

Dheeraj Sharma
Dheeraj Sharma
Numerade Educator
01:07

Problem 77

In the above problem, if the mains supply is $210 \mathrm{~V}$, then the current flowing in the geyser is
(a) $7.5 \mathrm{~A}$
(b) $2.5 \mathrm{~A}$
(c) $5.0 \mathrm{~A}$
(d) $10 \mathrm{~A}$

Mahipal Kumawat
Mahipal Kumawat
Numerade Educator
01:14

Problem 78

An electric heater operating at $220 \mathrm{~V}$ boils 5 litres of water in 5 minutes. If it is used on $110 \mathrm{~V}$ line, it will boil the same amount of water in
(a) $10 \mathrm{~min}$
(b) $20 \mathrm{~mm}$
(c) $5 \mathrm{~min}$
(d) none of these

Satpal Satpal
Satpal Satpal
Numerade Educator
01:33

Problem 79

An immersion heater is rated $418 \mathrm{~W}$. It should heat a litre of water from $10^{\circ} \mathrm{C}$ to $30^{\circ} \mathrm{C}$ in nearly
(a) $400 \mathrm{~S}$
(b) $200 \mathrm{~S}$
(c) $144 S$
(d) $100 \mathrm{~S}$

Mahipal Kumawat
Mahipal Kumawat
Numerade Educator
01:37

Problem 80

Two bulbs of equal wattage, one having carbon filament and the other having a tungsten filament, are connected in series to the mains. Then
(a) carbon filament bulb glows less
(b) carbon filament bulb glows more
(c) both bulbs glow equally
(d) tungsten filament bulb glows more

Hunza Gilgit
Hunza Gilgit
Numerade Educator
02:19

Problem 81

The water in an electric kettle begins to boil in ten minutes after being switched on. The wire used as the heating element is modified so that the water begins to boil in 7 minutes. Now,
(a) the length of the wire is increased
(b) the length of the wire is decreased
(c) another identical wire should be connected in series
(d) another identical wire should be connected in parallel

Shahab Ullah
Shahab Ullah
Numerade Educator
02:51

Problem 82

An electric heater and a fan are marked $1000 \mathrm{~W}, 220 \mathrm{~V}$ and $100 \mathrm{~W}, 220 \mathrm{I}$ "respectively. The resistance of fan is
(a) equal to that of heater
(b) greater than that of heater
(c) less than that of heater
(d) zero

Melissa Walsh
Melissa Walsh
Numerade Educator
01:17

Problem 83

You are given a resistance wire of length $100 \mathrm{~cm}$ and a battery of negligible internal resistance. In which of the following cases is the largest amount of heat generated?
(a) When the wire is divided in two parts and both the parts are connected to the battery in parallel.
(b) When the wire is connected to the battery directly.
(c) When the wire is divided into four parts and all the four parts are connected in parallel to the battery
(d) When only half of the wire is connected to the battery

Satpal Satpal
Satpal Satpal
Numerade Educator
00:54

Problem 84

When a current is passed in a conductor, $3^{\circ} \mathrm{C}$ rise in temperature is observed. If the strength of current is increased three times, then rise in temperature will approximately be
(a) $3^{\circ} \mathrm{C}$
(b) $9^{\circ} \mathrm{C}$
(b) $27^{\circ} \mathrm{C}$
(d) $36^{\circ} \mathrm{C}$

Varsha Aggarwal
Varsha Aggarwal
Numerade Educator
01:25

Problem 85

The temperature of hot junction of a thermocouple changes from $80^{\circ} \mathrm{C}$ to $100^{\circ} \mathrm{C}$. The percentage change in thermoelectric power is
(a) $8 \%$
(b) $10 \%$
(c) $20 \%$
(d) $25 \%$

Amita Prajapat
Amita Prajapat
Numerade Educator
01:12

Problem 86

In a thermocouple minimum current flows at
(a) neutral temperature
(b) temperature of inversion
(c) twice the neutral temperature
(d) twice the temperature of inversion

Satpal Satpal
Satpal Satpal
Numerade Educator
01:21

Problem 87

A battery is connected to a thermocouple of copper and iron. The two junctions will be
(a) at the sume temperature
(b) heated
(c) neither heated nor cooled
(d) undergoing thermoelectric effect leading to the heating of one junction and cooling of the other

Satpal Satpal
Satpal Satpal
Numerade Educator
03:59

Problem 88

The atomic mass number of zine is 66 and its valency is 2. The mass of zine liberated by $9.65 \mathrm{~A}$ of current in 10 sec will be
(a) $33 \mu \mathrm{g}$
(b) $33 \mathrm{mg}$
(c) $33 \mathrm{~g}$
(d) $33 \mathrm{~kg}$

Shalini Tyagi
Shalini Tyagi
Numerade Educator
01:23

Problem 89

If $100 \mathrm{KWh}$ of energy is consumed at $33 \mathrm{~V}$ in a copper voltameter, then the mass of copper liberated will be (given e.c.c. of $\mathrm{Cu}=0.33 \times 10^{-6} \mathrm{kgC}^{-1}$ )
(a) $3.3 \mathrm{~kg}$
(b) $3.6 \mathrm{~kg}$
(c) $1 \mathrm{~kg}$
(d) $1 \mathrm{mg}$

Satpal Satpal
Satpal Satpal
Numerade Educator
01:53

Problem 90

Which of the following is not the cause of low conductivity of electrolytes ?
(a) Low drift velocity of ions
(b) High resistance offered by the solution to the motion of ions
(c) Low number density of charge carriers
(d) Ionisation of salt

Satpal Satpal
Satpal Satpal
Numerade Educator
01:09

Problem 91

Current in an electrolyte is carried by
(a) only electrons
(b) only -ve ions
(c) only $+v e$ ions
(d) both $+v e$ and $-v e$ ions

Kim Trang Nguyen
Kim Trang Nguyen
Numerade Educator
01:06

Problem 92

A box with two terminals is connected in series with a $2 \mathrm{~V}$ battery, an ammeter and a switch. When the switch is closed, the needle of the ammeter moves quickly across the scale and then drops back to zero. The box contains
(a) a $50 \Omega$ resistance
(b) a copper strip
(c) a diode
(d) a small length of fuse wire

Narayan Hari
Narayan Hari
Numerade Educator