An electrically isolated conducting ring surrounds an electromagnet. A magnetic field sensor is placed at the centre of the ring. When the current in the electromagnet increases, the sensor records a smaller increase in magnetic field when the ring is unbroken than when the ring has a narrow gap.
Which statement explains why?
Current passes from the electromagnet into the ring and produces an opposing magnetic field.
The changing field induces a current in the unbroken ring whose magnetic field reinforces the increase.
The changing field induces a current in the unbroken ring whose magnetic field opposes the increase.
The gapped ring carries an induced current whose magnetic field opposes the increase.
96 exam-style questions on AQA GCSE Physics 7.3 Induced potential, transformers and the National Grid (HT only), covering 7.3.1 Induced potential (HT only), 7.3.2 Uses of the generator effect (HT only), 7.3.3 Microphones (HT only), and 7.3.4 Transformers (HT only). Each one has a worked solution and a mark scheme showing where the marks go.