What will be the frequency of an alternating current if its direction changes after every $0.01\,s$ (in $,Hz$)?

Inside a solenoid,the magnetic field is constant in magnitude and direction.

The diagram below shows two ways of connecting three bulbs $A, B$ and $C$ to a $220 \,V$ main in a room. Name the two arrangements. Which of them would you prefer for household electricity? Give two reasons.

What is the nature of the magnetic field lines passing through the center of a current-carrying circular loop?

Who first observed the magnetic effect of an electric current?

Can a freely suspended current-carrying solenoid stay in any direction? Justify your answer. What will happen when the direction of current in the solenoid is reversed? Explain.