Direct-current circuits | Practice Problems, Examples & Solutions

Resistors in Series and Parallel

University Physics

The power rating of a resistor used in ac circuits refers to the maximum average power dissipated in the resistor. How does this compare with the maximum instantaneous power dissipated in the resistor?

Alternating-Current Circuits

03:05

University Physics

Semi-tractor trucks use four large $12-\mathrm{V}$ batteries. The starter system requires 24 V, while normal operation of the truck's other electrical components utilizes 12 V. How could the four batteries be connected to produce 24 V? To produce 12 V? Why is 24 V better than 12 V for starting the truck's engine (a very heavy load)?

Direct-Current Circuits

02:25

University Physics

What are the advantages and disadvantages of connecting batteries in series? In parallel?

Direct-Current Circuits

Kirchhoff’s Rules

46 Practice Problems

07:58

Physics for Scientists and Engineers

Consider the circuit shown in Figure P28.9. Find
(a) the current in the $20.0-\Omega$ resistor and (b) the potential difference between points $a$ and $b$
FIGURE CANT COPY

Direct Current Circuits

06:41

Physics for Scientists and Engineers

A lightbulb marked "75 W [at] $120 \mathrm{V}^{\text {m }}$ is screwed into a socket at one end of a long extension cord, in which each of the two conductors has resistance $0.800 \Omega .$ The other end of the extension cord is plugged into a $120-\mathrm{V}$ outlet. Draw a circuit diagram and find the actual power delivered to the bulb in this circuit.

Direct Current Circuits

01:43

Conceptual Physics

Three 6-ohm resistors are arranged in a triangle as shown. A voltage source of 12 V is impressed across one of the resistors.
(a) How much current is in that resistor?
(b) How much current is in each of the other two resistors?
(c) How much current is in the voltage source?
(d) What is the equivalent resistance of the circuit (what single resistor connected to the voltage source could replace the three resistors)?

Electric Current

R-C Circuits

43 Practice Problems

04:02

Physics

(a) What is the reactance of a 5.00 - $\mu \mathrm{F}$ capacitor at the frequencies $f=12.0 \mathrm{Hz}$ and $1.50 \mathrm{kHz} ?$ (b) What is the impedance of a series combination of the $5.00-\mu \mathrm{F}$ capacitor and a $2.00-\mathrm{k} \Omega$ resistor at the same two frequencies? (c) What is the maximum current through the circuit of part (b) when the ac source has a peak voltage of $2.00 \mathrm{V} ?$ (d) For each of the two frequencies, does the current lead or lag the voltage? By what angle?

Alternating Current

02:36

Physics

A capacitor and a resistor are connected in parallel across an ac source. The reactance of the capacitor is equal to the resistance of the resistor. Assuming that $i_{\mathrm{C}}(t)=I \sin \omega t,$ sketch graphs of $i_{\mathrm{C}}(t)$ and $i_{\mathrm{R}}(t)$ on the
same axes.

Alternating Current

03:36

Holt Physics

Which of the switches in the circuit below will complete a circuit when closed? Which will cause a short circuit?
(FIGURE CANNOT COPY)

Circuits and Circuit Elements

Power Distribution Systems

20 Practice Problems

01:15

University Physics

Can the instantaneous power output of an ac source ever be negative? Can the average power output be negative?

Alternating-Current Circuits

02:58

University Physics

The average ac current delivered to a circuit is zero. Despite this, power is dissipated in the circuit. Explain.

Alternating-Current Circuits

01:45

University Physics

Do batteries in a circuit always supply power to a circuit, or can they absorb power in a circuit? Give an example.

Direct-Current Circuits