A potentiometer is essentially a resistor with three...

A potentiometer is essentially a resistor with three contacts, one of which is mobile. It acts as a variable resistor, since changing the position of the mobile contact, called the "wiper" (denoted by an arrow), changes the amount of the resistor through which current must pass. The circuit shown consists of one 82.6 V battery, one fixed resistor with resistance R1 = 1480 Ω, and one potentiometer. In addition, one of the wires is grounded (at zero potential). The resistive material inside the potentiometer has a resistance of 425 Ω/mm. To what distance x should the wiper be moved so that 14.8 mA of current passes through point B? x = mm With the wiper in this position, what is the potential at point B?

Transcript

00:01 In this question we are doing solving for a potential meter so a potential meter is basically a variable resistor so this will be this variable resistor that we have so we move this point of contact and the circuit becomes like this so this part of this resistance will not be in use and we will we can use the required length of the resistor in our circuit so we can change the resistance.

00:29 So, this is a variable resistor.

00:32 So in this question we are given this circuit.

00:34 The battery is of 82 .6 volts and this point is at ground.

00:39 Then we have a fixed to resistance r1 of 1480 oms.

00:44 Then we have this point b and let's say this is the resistance that we have and this resistor.

00:53 So if we say that the resistance of this point that, that we have, that we say that, we have inside the circuit it will it is given as 425 oms per millimeter so the resistance for this is given as per millimeter so we can multiply multiplied by the length in millimeter so that there is tens per unit length was given as 425 oms per millimeter so we can say that this resistance r is 425 multiplied by x oms where x is in millimeters.

01:31 So now we know everything so we have to find out first of all the value for the x so the length x that we should have such that the current flowing in the circuit is 14 .8 millie -amperors and we have to tell the potential at this point b so let us say this is our point a and this point of contact is our point c so we know the three points.

01:57 So point a is at zero potential.

01:59 It is on ground.

02:00 So we can say at this point also it will be zero volts.

02:03 So battery is there.

02:05 So if the positive of the battery is at zero, so the negative of the battery will be at minus 82 .6 volts.

02:12 So we can say that v, this will be same as the potential at c.

02:18 Vc is minus 82 .6 volts and the potential at point a is zero volts...