NESA Physics Applications of the Motor Effect
1 sample question with marking guides and sample answers · Avg. score: 0%
Denzil is using a demonstration hand-cranked generator.
A schematic diagram of the generator is shown in Figure 17. The generator contains a rectangular coil with side lengths of 5.0 cm and 2.5 cm, consisting of 20 turns of insulated copper wire. The coil is rotated between two bar magnets that provide a field strength of 0.60 T between the magnets.
Denzil rotates the coil at a frequency of 50 Hz.
State why the flux through the coil changes as the coil rotates.
Reveal Answer
The flux through the coil is determined by the angle between the plane of the coil and the magnetic field.
| Descriptor | Marks |
|---|---|
States that the angle or orientation between the plane of the coil and the magnetic field changes | 1 |
Show that the change in flux as the coil rotates from a horizontal to a vertical position is .
Reveal Answer
| Descriptor | Marks |
|---|---|
Demonstrates correct substitution into the magnetic flux formula (e.g., ) | 1 |
Calculate the average EMF induced as the coil is rotated through a quarter turn from a horizontal to a vertical position.
Reveal Answer
| Descriptor | Marks |
|---|---|
Calculates the correct time for a quarter turn () | 1 |
Substitutes values correctly into Faraday's law formula () | 1 |
Calculates the correct average EMF of | 1 |
State a change to the set-up in Figure 17 that could produce a DC output from the generator. Give a reason for your choice.
Reveal Answer
Replace the slip rings with a split-ring commutator. The split-ring commutator will reverse the connections to the loop every half turn to ensure a DC output.
| Descriptor | Marks |
|---|---|
Identifies replacing the slip rings with a split-ring commutator | 1 |
Explains that the split-ring commutator reverses the connections to the loop every half turn to ensure a DC output | 1 |