1.
How much charge flows through an appliance rated 240V, 60W when it is used for 5 mins?
Correct Answer
A. 75.0 C
Explanation
The correct answer is 75.0 C. Charge is calculated by multiplying the current (I) by the time (t). In this case, the power (P) is given as 60W, and since P = IV, we can calculate the current as I = P/V. Plugging in the values, I = 60W/240V = 0.25A. Given that the time is 5 minutes (or 300 seconds), we can calculate the charge as Q = It = 0.25A * 300s = 75.0 C.
2.
The e.m.f of a cell is 1.5V. What energy is dissipated by the cell if it drives 0.4C of charge round the circuit?
Correct Answer
A. 0.6 J
Explanation
The energy dissipated by the cell can be calculated using the formula E = QV, where E is the energy, Q is the charge, and V is the voltage. In this case, the charge is 0.4C and the voltage is 1.5V. Plugging these values into the formula, we get E = 0.4C * 1.5V = 0.6 J. Therefore, the correct answer is 0.6 J.
3.
What is the e.m.f of a cell if it uses 4.2 joules of energy as it pushes 6 coulombs of charge around a circuit?
Correct Answer
A. 0.7 V
Explanation
The electromotive force (e.m.f) of a cell is a measure of the energy provided by the cell to each unit of charge that passes through it. In this question, the cell uses 4.2 joules of energy to push 6 coulombs of charge around the circuit. To find the e.m.f, we divide the energy (4.2 J) by the charge (6 C), which gives us 0.7 V. Therefore, the correct answer is 0.7 V.
4.
What is electrical energy converted as heat by a 240 V light bulb that is switched on for 300 seconds? A current of 5A is moving through the bulb.
Correct Answer
A. 360000 J
Explanation
The electrical energy converted as heat by a light bulb can be calculated using the formula: Energy = Power × Time. In this case, the power can be calculated using the formula: Power = Voltage × Current. Given that the voltage is 240V and the current is 5A, we can calculate the power as 240V × 5A = 1200W. Finally, multiplying the power by the time of 300 seconds gives us the total energy converted as heat: 1200W × 300s = 360000 J. Therefore, the correct answer is 360000 J.
5.
What is the power of a light bulb if a 240 V light bulb is switched on for 2 minutes?
A current of 3 A is moving through the bulb.
Correct Answer
A. 720 Watts
Explanation
The power of a light bulb can be calculated using the formula P = VI, where P is power, V is voltage, and I is current. In this case, the voltage is given as 240 V and the current is given as 3 A. By substituting these values into the formula, we get P = 240 V * 3 A = 720 Watts. Therefore, the power of the light bulb is 720 Watts.