Units (Magnetism & Electromagnetism)
5 marks · NormalBelow is a table showing the currents and voltages measured for a simple circuit containing a solenoid. The power supplied is also included.
| Current (A) | Voltage (V) | Power (W) |
|---|---|---|
| 0.50 | 3.0 | 1.5 |
| 0.80 | 5.0 | 4.0 |
| 1.20 | 7.5 | 9.0 |
State the unit for power, and explain how the power values are calculated using current and voltage.
If you wanted to make the electromagnet in the solenoid stronger, explain two changes you could make to increase the power supplied to it.
Work this out on paper, then compare with the answer and worked solution below. With a free account you can submit written answers for marking.
Show answer
(a) Power is measured in watts (W). Power is calculated by multiplying current (A) by voltage (V).
(b) Increase the current or the voltage supplied to the solenoid, or increase the number of turns on the coil/solenoid, or use an iron core.
Also accept: Increasing current or voltage; Adding more turns to the solenoid
Show mark scheme and worked solution
Marking points
B1 (a) · 1 mark · Correctly states power unit: watt (W).
M1 (a) · 1 mark · States or uses P = I × V.
B2 (b) · 1 mark · Mentions increasing current (or voltage) increases power and field strength.
B3 (b) · 1 mark · States increasing number of turns on solenoid also increases field strength.
B4 (b) · 1 mark · Alternative: using a magnetically soft iron core increases the field strength.
Worked solution
a) Power in watts (W) is calculated as P = I × V.
b) Two ways to increase the power supplied (and thus the electromagnet strength): (1) increase the current; (2) increase the voltage. Alternatively, use more turns of wire, or an iron core.