Electromagnetism | OCR A-Level Physics A (H556)
Electromagnetism
- 67 questions
- 6 subtopics
- Module 6: Particles and medical physics
- Paper 2 and Paper 3
Magnetic fields and what moves in them: the motor effect, charged particles in a field, magnetic flux and Faraday's law, and the transformer..
It covers magnetic fields and field patterns, fleming's left-hand rule and the motor effect, magnetic flux density and the tesla, charged particles in magnetic fields, magnetic flux, flux linkage and Faraday's law and transformers and the a.c. generator.
Sample questions from Electromagnetism
Answer each one closed book first, then open the answer.
-
Magnetic fields and field patterns
What do magnetic field lines represent in terms of direction and strength?
Show the answer
Magnetic field lines show the direction of the field (tangent to the line at any point) and their spacing indicates relative strength—closer lines mean a stronger field. -
Magnetic fields and field patterns
Describe the magnetic field inside a long solenoid.
Show the answer
The field inside is uniform and parallel to the axis of the solenoid. -
Fleming's left-hand rule and the motor effect
In the current-balance experiment to measure magnetic flux density, how is the wire positioned relative to the magnet poles?
Show the answer
A wire of known length is placed horizontally between the poles of the magnet, perpendicular to the field. -
Fleming's left-hand rule and the motor effect
What is recorded when current flows through the wire in the current-balance experiment?
Show the answer
The change in mass reading on the digital balance. -
Magnetic flux density and the tesla
Define one tesla in terms of force, current and length.
Show the answer
One tesla is the magnetic flux density when a wire carrying a current of one ampere, perpendicular to the field, experiences a force of one newton per metre of its length. -
Magnetic flux density and the tesla
What are the key features of a search coil used to investigate magnetic flux?
Show the answer
It is a small coil of known area and known number of turns. -
Charged particles in magnetic fields
How is the expression r = mv/(BQ) derived?
Show the answer
By equating the magnetic force BQv to the centripetal force mv²/r and rearranging for r. -
Charged particles in magnetic fields
State the expression for the velocity of particles selected by a velocity selector.
Show the answer
v = E/B, where E is electric field strength and B is magnetic flux density.
The 6 subtopics
One subtopic is one session. Work down the list.
| Subtopic | What it covers | Questions |
|---|---|---|
| Magnetic fields and field patterns | Recall questions on sources of magnetic fields, field lines, the field patterns of a straight wire, a flat coil and a solenoid, and finding the direction of the field around a wire. | 8 |
| Fleming's left-hand rule and the motor effect | Recall questions on Fleming's left-hand rule, the force on a current-carrying conductor F = BIL sin θ with calculations, and the current-balance experiment to measure magnetic flux density. | 12 |
| Magnetic flux density and the tesla | Recall questions on defining magnetic flux density and the tesla, magnetic flux and its calculation, and measuring flux density with a search coil. | 8 |
| Charged particles in magnetic fields | Recall questions on the force on a charged particle in a magnetic field, circular paths and r = mv/BQ, velocity selectors, and calculations of force, orbit radius and selected velocity. | 13 |
| Magnetic flux, flux linkage and Faraday's law | Recall questions on the weber, magnetic flux linkage, Faraday's law and Lenz's law, calculating induced e.m.f., and changing the flux linkage through a search coil. | 8 |
| Transformers and the a.c. generator | Recall questions on how an a.c. generator produces a sinusoidal e.m.f., slip rings and brushes, how a transformer works, its core, the turns-ratio equations with calculations, and investigating transformers. | 18 |
How the guide is worked
Answering a question from memory stores it far better than reading the answer again. The guide runs that as a fixed procedure on one subtopic at a time, about twenty minutes a session.
-
Step 1 · Closed book
Cover the answers. Work through one subtopic and write down what you can. Leave blanks where you have nothing.
-
Step 2 · Open book
Go back to the top. Read each printed answer and write it out in full, including the ones you had right.
-
Step 3 · Closed book again
Same questions, same order, from memory. The gap between pass one and pass three is the session result.
Read the full method, the return schedule and the research behind it.
Nearby topics
OCR A-Level Physics A Active Recall Guide
Every topic, not just this one. 1,862 questions with their answers.