Back to Directory
NEET PHYSICSMedium

Consider a simple circuit shown in the figure. R' stands for variable resistance. R' can vary from R₀ to infinity. r is the internal resistance of the battery (r<<R<<R₀). (a) Potential drop across AB is nearly constant as R' is varied. (b) Current through R' is nearly constant as R' is varied. (c) Current I depends sensitively on R'. (d) I ≥ V/(r+R) always.

Which among the following statements is correct?

A

(a) and (c)

B

(a) and (d)

C

(b) and (d)

D

(c) and (d)

Step-by-Step Solution

Since R' is connected in parallel with R and R' varies from R₀ to infinity (where R << R₀), the equivalent resistance of the parallel combination (R || R') remains slightly less than R but close to R.

  1. Current I (Statement d): The total resistance of the circuit is r + (RR'/(R+R')). Since the parallel combination is always less than R, the total resistance is less than r + R. Consequently, the total current I = V / R_total will be greater than or equal to V / (r + R). Thus, statement (d) is correct.
  2. Potential Drop (Statement a): The potential drop across AB is V_AB = V - Ir. Since I is determined primarily by R (as R' is large) and r is small, I is nearly constant, making V_AB nearly constant. Thus, statement (a) is correct.
  3. Current through R' (Statement b): The current through R' is V_AB / R'. Since V_AB is constant and R' varies significantly, the current through R' varies inversely with R' and is not constant.
Practice Mode Available

Master this Topic on Sushrut

Join thousands of students and practice with AI-generated mock tests.

Get Started
Solved: PHYSICS Question for NEET | Sushrut