Concepts Of Physics MCQ Edition [Volume 2]

Exam: Concepts Of Physics MCQ Edition [Volume 2]
Subject: Physics
Chapter: Electric Current in Conductors

Concepts Of Physics MCQ Edition [Volume 2] · Physics · Electric Current in Conductors

A battery with an emf of 100 V and a resistor having a resistance...

A battery with an emf of

100 \text{ V}

and a resistor having a resistance of

10 \text{ k}\Omega

are connected in series. This arrangement serves as a source to deliver current to an external resistance

R

. Provided that

R

does not exceed

100 \Omega

, the current flowing through it remains constant up to two significant digits. Determine the value of this current. (This illustrates the fundamental principle of a constant-current source.)

Options

A $0.001 \text{ A}$
B $1 \text{ A}$
C $0.1 \text{ A}$
D $0.01 \text{ A}$

Correct answer

D. $0.01 \text{ A}$

Step-by-step solution

The total resistance of the circuit is

R_{eq} = 10 \text{ k}\Omega + R = 10000 + R

.

Since

R \le 100 \Omega

, we have

R \ll 10000 \Omega

.

Therefore, the equivalent resistance is approximately

R_{eq} \approx 10000 \Omega

.

The current flowing through the external resistance is given by Ohm's law:

I = \dfrac{E}{R_{eq}} \approx \dfrac{100}{10000} = 0.01 \text{ A}

This current remains approximately constant for small values of

R

, acting as a constant-current source.

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