Question

An ammeter of resistance 20 \( \Omega \) gives full scale deflection when 1 mA current flows through it. What is the maximum current that can be measured by connecting 4 resistors each of 16 \( \Omega \) in parallel with the meter?

• A. 6 mA
• B. 8 mA
• C. 4 mA
• D. 2 mA

Hint:

When resistors are connected in parallel, the equivalent resistance decreases, which increases the maximum measurable current.

Answer 1

The Correct Option is C

Step 1: Equivalent resistance of parallel resistors.
The equivalent resistance \( R_{\text{eq}} \) of 4 resistors each of resistance \( 16 \, \Omega \) in parallel is: \[ R_{\text{eq}} = \frac{R}{4} = \frac{16}{4} = 4 \, \Omega \]
Step 2: Using Ohm’s Law.
The total resistance in the circuit is \( 20 + 4 = 24 \, \Omega \). The maximum current is given by: \[ I = \frac{V}{R} = \frac{1 \, \text{mA} \times 24 \, \Omega}{20 \, \Omega} = 4 \, \text{mA} \]
Step 3: Conclusion.
Thus, the maximum current is (C) 4 mA.