A 100% efficient transformer converts a 120 V input voltage to a 6.0 V output voltage. The output power of the transformer can be a maximum of 30 W.
The output is connected to three 0.40 A bulbs in parallel. One of the bulbs fails.
How does the current in the primary coil change?
It decreases by 0.40 A0.40\text{ A}0.40 A.
It decreases by 0.020 A0.020\text{ A}0.020 A.
It increases by 0.020 A0.020\text{ A}0.020 A.
It remains unchanged.
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.