A cell of emf 90 V is connected across series combination of two resistors each of resistance. A voltmeter of resistance is used to measure the potential difference across each resistor. The reading of the voltmeter will be :
- A.45 V
- B.80 V
- C.90 V
- D.40 V
Show answer and solution
Correct option: D
Solution
The voltmeter (400Ω) in parallel with one 100Ω resistor gives an effective resistance of (400×100)/(400+100) = 80Ω. The circuit now has 80Ω and 100Ω in series across 90V. Current from cell = 90/(80+100) = 0.5A. Voltmeter reading = 0.5 × 80 = 40V.
[JEE Main 2023 · 24 Jan · Shift 2]