The voltage supplied to a DC electric motor is reduced, which decreases the current in the coil. Which row in the table describes two modifications that could be made to keep the motor running at its original speed?
| Strength of the magnets | Number of turns on the coil | |
|---|---|---|
| A | decrease | decrease |
| B | decrease | increase |
| C | increase | decrease |
| D | increase | increase |
Row A: decrease the strength of the magnets, decrease the number of turns
Row B: decrease the strength of the magnets, increase the number of turns
Row C: increase the strength of the magnets, decrease the number of turns
Row D: increase the strength of the magnets, increase the number of turns
275 exam-style questions on CIE IGCSE Physics 4.5 Electromagnetic effects, covering 4.5.1a Electromagnetic induction, 4.5.1b Direction of an induced e.m.f., 4.5.2 The a.c. generator, 4.5.3a Magnetic effect of a current and its applications, 4.5.3b Strength and direction of the field around wires and solenoids, 4.5.4a Force on a current-carrying conductor, 4.5.4b Force on beams of charged particles, 4.5.5 The d.c. motor, 4.5.6a Construction and operation of a transformer, 4.5.6b Turns ratio and current in a transformer, and 4.5.6c High-voltage transmission of electricity. Each one has a worked solution and a mark scheme showing where the marks go.