Questions
Draw the time graph of direct current and alternating current.
The frequency of a.c. in our country is 50 Hz, what does it mean?
Transformers are used in mobile chargers. Give reason(s).
The core of a transformer is laminated. Why?
The number of primary windings and secondary windings of a transformer are not the same.
An electromagnet is used in the electric bell. Give reason.
When a magnetic compass is placed near a circuit in which an electric current is flowing, its needle deflects. Why?
When a ceiling fan is connected to the circuit of the solar panel, the fan does not rotate. Why?
There are 1000 components in a box of which 10 are known to be defective. Two components are selected at random. What is the probability that:
- both are defective
- neither are defective
- just one is defective? (Do not simplify your answer)
Pot A contains 3 red balls and 1 white ball. Pot B contains 2 red balls and 3 white balls. A ball is chosen at random from each bag in turn. Find the probability of taking:
- a white ball from each pot.
- two balls of the same colour.