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An induction hob consists of a coil beneath a sheet of ceramic material - Edexcel - A-Level Physics - Question 11 - 2023 - Paper 1
Question 11
An induction hob consists of a coil beneath a sheet of ceramic material. The coil is connected to an alternating current (a.c.) supply as shown. (a) A steel pan con... show full transcript
Worked Solution & Example Answer:An induction hob consists of a coil beneath a sheet of ceramic material - Edexcel - A-Level Physics - Question 11 - 2023 - Paper 1
Step 1
A steel pan containing water is placed on the induction hob. Explain why the pan becomes hot when the supply is switched on.
Answer
When the a.c. supply is turned on, electric current flows through the coil beneath the ceramic sheet. This current generates a magnetic field around the coil. As the alternating current changes direction, it produces a fluctuating magnetic field that permeates the pan placed above.
The changing magnetic field induces an electromotive force (emf) in the steel pan, which is a conductive material. This induced emf causes a current to flow within the pan, resulting in Joule heating (I²R losses) due to the resistance of the pan's material. Consequently, as the current heats up the pan, it transfers heat to the water inside, causing it to heat up as well.
Step 2
The a.c. supply to the coil in an induction hob has a much higher frequency than normal mains frequency. Explain why this is an advantage in this case.
Answer
Using a higher frequency a.c. supply in an induction hob enhances the efficiency of induction heating. Higher frequency results in a faster changing magnetic field, which induces a more substantial current in the pan. This leads to improved heating performance as the pan heats up more quickly compared to using a lower frequency supply. Additionally, higher frequencies can reduce the energy loss in the process, making induction cooking more efficient overall.