Name two safety measures commonly used in electric circuits and appliances. What precautions should be taken to avoid the overloading of domestic electric circuits?

$(i)$ The given figure shows a domestic electric circuit. Study this circuit carefully. List any two errors in the circuit and justify your answer.
$(ii)$ Give one difference between the wires used in the element of an electric heater and in a fuse:
$(iii)$ List two advantages of parallel connection over series connection.

An alternating electric current has a frequency of $50 \, Hz$. How many times does it change its direction in one second? Give reason for your answer.

Which of the following is used in a fire alarm?

What is the role of a fuse used in series with any electrical appliance? Why should a fuse with a defined rating not be replaced by one with a larger rating?

What is the function of an earth wire? Why is it necessary to earth metallic appliances?