Science — CBSE Class 10 board question

(Note: Since exact resistor values are not visible in the diagram, I am using standard textbook values: Arm A has two resistors of 1 Ω and 2 Ω in series; Arm B has 4 Ω; Arm C has 4 Ω.)

(a) Equivalent resistance of Arm A:

$$R_A = 1 + 2 = 3 \ \Omega$$

(b) Equivalent resistance of parallel combination of Arms B and C:

$$\frac{1}{R_{BC}} = \frac{1}{4} + \frac{1}{4} = \frac{2}{4} = \frac{1}{2}$$

$$R_{BC} = 2 \ \Omega$$

(c) Total equivalent resistance of the circuit:

$$R_{total} = R_A + R_{BC} = 3 + 2 = 5 \ \Omega$$

If battery voltage = 5 V:

$$I = \frac{V}{R} = \frac{5}{5} = 1 \ \text{A}$$

The ammeter reads 1 A.

Source: Chapter 11 – Electricity, CBSE Class 10 Science

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• Since the diagram values are not available, standard textbook values are assumed. In the actual exam, substitute the given values.
• Part (a): Resistors in series → simply add them.
• Part (b): Resistors in parallel → use the reciprocal formula $\frac{1}{R} = \frac{1}{R_1} + \frac{1}{R_2}$.
• Part (c) typically asks for total resistance or current — apply Ohm's Law: $V = IR$.
• Always show formula, substitution, and final answer with units.