The electric current that always flows in the same direction is called alternating current.

$(a)$ Describe an activity to determine the direction of magnetic field produced by a current-carrying straight conductor. Also,show that the direction of the magnetic field is reversed on reversing the direction of current.
$(b)$ An $\alpha$-particle (which is a positively charged particle) enters a uniform magnetic field at right angles to it as shown below. Stating the relevant principle,explain in which direction will this $\alpha$-particle move?

The principle of which of these devices is based on electromagnetism?

Identify the type of magnetic fields represented by the magnetic field lines given below and name the type of conductors which can produce them.

$A$ student,while studying the force experienced by a current-carrying conductor in a magnetic field,records the following observations:
$(i)$ The force experienced by the conductor increases as the current is increased.
$(ii)$ The force experienced by the conductor decreases as the strength of the magnetic field is increased.
Which of the two observations is correct and why?

According to Fleming's right-hand rule,what is indicated by the direction of the center finger?