Circuits — Set 1
Physics · परिपथ · Questions 1–10 of 50
Two resistors of 2 Ω and 3 Ω are connected in series. What is the equivalent resistance?
Correct Answer: A. 5 Ω
In series, resistances add, so R = 2 + 3 = 5 Ω. The same current flows through each series resistor. Series connection increases total resistance and reduces current for a fixed voltage.
Two resistors of 6 Ω and 3 Ω are connected in parallel. What is the equivalent resistance?
Correct Answer: A. 2 Ω
For parallel resistors, 1/R = 1/6 + 1/3 = 1/6 + 2/6 = 1/2 so R = 2 Ω. In parallel, the voltage across each branch is the same. Equivalent resistance in parallel is always less than the smallest branch resistance.
A 12 V cell with internal resistance 1 Ω is connected to a 5 Ω resistor. What current flows in the circuit?
Correct Answer: D. 2 A
Total resistance is R + r = 5 + 1 = 6 Ω, so I = E/(R+r) = 12/6 = 2 A. Internal resistance reduces the current compared to an ideal cell. Terminal voltage becomes lower than emf when the cell delivers current.
A current of 3 A flows through a 4 Ω resistor. What power is dissipated in the resistor?
Correct Answer: A. 36 W
Power in a resistor is P = I^2R, so P = 3^2 × 4 = 36 W. This electrical power is converted mainly into heat in the resistor. The unit watt equals joule per second.
A 10 V supply is connected across 2 Ω and 3 Ω in series. What is the potential difference across the 3 Ω resistor?
Correct Answer: A. 6 V
In a series divider, V across 3 Ω is V = 10 × 3/(2+3) = 6 V. Series resistors share voltage in proportion to their resistances. A potential divider is widely used to obtain a desired fraction of a voltage.
Which statement is correct for Kirchhoff’s current law at a junction?
Correct Answer: A. Sum of currents entering equals sum leaving
Kirchhoff’s current law says the total current entering a junction equals the total leaving it. This follows from conservation of electric charge. It is used to analyze complex branching circuits.
Which statement is correct for Kirchhoff’s voltage law in a closed loop?
Correct Answer: B. Algebraic sum of potential differences is zero
Kirchhoff’s voltage law states that the algebraic sum of all potential differences around a closed loop is zero. It is a result of conservation of energy in circuits. This rule is applied while writing loop equations for networks.
A Wheatstone bridge is balanced when which condition is satisfied?
Correct Answer: A. P/Q = R/S
A Wheatstone bridge is balanced when the ratio P/Q equals R/S. At balance, no current flows through the galvanometer branch. This condition is used to find an unknown resistance accurately.
An ideal ammeter should be connected how, and should have what resistance?
Correct Answer: D. In series and very low resistance
An ammeter is connected in series so the same current passes through it and the circuit part. It should have very low resistance to avoid changing the current. Real ammeters are made using a galvanometer with a shunt resistor.
An ideal voltmeter should be connected how, and should have what resistance?
Correct Answer: D. In parallel and very high resistance
A voltmeter is connected in parallel across the component whose voltage is measured. It should have very high resistance so it draws negligible current. Real voltmeters are made by adding a high series resistance to a galvanometer.