An electric heating mat, Mat X, is used to maintain the temperature of a cell culture chamber in a biology laboratory. It contains an electrical heating element.
Mat X is designed to operate on the mains supply and is labelled 240 V240\text{ V}240 V, 120 W120\text{ W}120 W.
What does 120 W tell you about how energy is transferred in the heating mat?
Mat X has a metallic outer casing and an earth connection. Explain how the earth connection protects the user.
Mat Y is connected to a low-voltage DC power supply. It is labelled 12 V12\text{ V}12 V, 42 W42\text{ W}42 W.
A student says: "I think that both mats should be fitted with a 3 A3\text{ A}3 A fuse."
Use calculations to evaluate this statement.
There is a step-down transformer in the power supply for Mat Y. Describe the structure of a step-down transformer.