Advertisements
Advertisements
Question
60 joules of heat was dissipated in a resistor when 20 C flowed for 5 s. Calculate:
(a) P.d. across the resistor,
(b) Resistance of the resistor, and
(c) Average power dissipated in the resistor.
Advertisements
Solution
Given, heat dissipated= 60 joules, charge Q = 20 C, time t= 5s
(a) P.d. across the rsistor, V = `"W"/"Q"= 60/20 = 3 "V"`
(b) Power = `"W"/"t" = "V"^2/"R"`
R = `"V"^2 xx "t"/"W" = (3)^2 xx 5/60 = 0.75 Omega`
(c) Power dissipated, P = `"W"/"t" = 60/5 = 12 "watt"`
APPEARS IN
RELATED QUESTIONS
A battery of 9 V is connected in series with resistors of 0.2 Ω, 0.3 Ω, 0.4 Ω, 0.5 Ω and 0.12 Ω. How much current would flow through the 12 Ω resistor?
In the circuit shown below, the voltmeter reads 10 V.
(a) What is the combined resistance?
(b) What current flows?
(c) What is the p.d. across 2 Ω resistor?
(d) What is the p.d. across 3 Ω resistor?
A battery and three lamps are connected as shown:
Which of the following statements about the currents at X, Y and Z is correct?
(a) The current at Z is greater than that at Y.
(b) The current at Y is greater than that at Z.
(c) The current at X equals the current at Y.
(d) The current at X equals the current at Z.
Draw a circuit diagram to show how two 4 V electric lamps can be lit brightly from two 2 V cells.
Ten bulbs are connected in a series circuit to a power supply line. Ten identical bulbs are connected in a parallel circuit to an identical power supply line.
(c) In which circuit, if one bulb blows out, all other will stop glowing?
Consider the circuit given below when A, B and C are three identical light bulbs of constant resistance. 
(a) List the bulbs in order of increasing brightness.
(b) If C burns out, what will be the brightness of A now compared with before?
(c) If B burns out instead, what will be the brightness of A and C compared with before?
A bulb marked 12 V, 24 W operates on a 12 volt car battery for 20 minutes. Calculate:
(i) The current flowing through it, and
(ii) The energy liberated.
State whether the current is a scalar or vector?
Calculate the current in a wire if a charge of 1500 coulomb flows through it in 5 minutes.
