GCSE Physics Question Analysis Topic: Physics - Electricity
Exam Question:
One morning an old man walked bare-foot to replace the fuse wire in kit kat fitted with power supply mains for his house. Suddenly he screamed and collapsed on the floor. His wife cried loudly for help. His neighbour's son Anil heard the cries and rushed to the place with shoes on. He took a wooden baton and used it to switch off the main supply.
Answer the following questions :
(i) What is the voltage and frequency of mains supply in India?
(ii) These days most of the electrical devices we use require a.c. voltage. Why?
(iii) Can a transformer be used to step up d.c. voltage?
(iv) Write two qualities displayed by Anil by his actions.
Answer:
For GCSE Physics, you should know:
(i)
The voltage of mains supply in India is 220 V rms and frequency is 50 Hz.
(ii)
Since most of the devices are used on mains supply which supplies a.c. voltage, they are designed to be used with a.c. voltage.
(iii)
Transformer can only step-up and step-down a.c. voltages as transformer comprises of inductors. Transformer secondary only creates voltage when a fluctuating flux is passed through it in accordance with:
e = - dϕ / dt
In a d.c. voltage system, ϕ is constant. As such, utilising secondary coils would not induce voltage.
(iv)
Anil displays two qualities, namely:
1) Preventing himself from being electrocuted by putting on wooden shoes.
2) Cutting off the mains power to stop the elderly man from acting as an earthing conductor.
Work hard for your GCSE Physics examination!
End of analysis. Great!
