Two insulated coils share an iron core. The primary coil is connected to a battery through a switch. A voltage sensor is connected across the secondary coil.
The sensor records a brief positive pulse when the switch is closed and a brief negative pulse when it is opened. It records zero while the primary current is steady.
Which explanation accounts for all three observations?
The field reverses, stays constant and reverses; induction depends on the presence of a field.
Charge enters, remains inside and leaves the core; induction depends on charge crossing the core.
The coils heat, stay warm and cool down; induction depends on the temperature of the coils.
The field increases, stays constant and decreases; induction depends on the change in field.
108 exam-style questions on Edexcel GCSE Physics 13.2 Transformers and the National Grid, covering 13.2.1 Transformers and induction, 13.2.2 The transformer turns-ratio equation, 13.2.3 The National Grid, 13.2.4 The transformer power equation, and 13.2.5 Advantages of high-voltage transmission. Each one has a worked solution and a mark scheme showing where the marks go.