An alternating electric current has a frequency of $50 \ Hz$. How many times does it change its direction in one second (in $times$)?

Identify the poles of the magnet in the given figure.

Describe an activity with a neat diagram to show the magnetic field lines around a bar magnet.

$A$ uniform magnetic field is directed vertically upwards. In which direction should an $\alpha$-particle (which is a positively charged particle) be projected in this field so that it is deflected southwards? Name and state the rule used to find the direction in this case.

State the condition for electromagnetic induction to take place. $A$ cylindrical bar magnet is kept along the axis of a circular coil as shown in the figure. Will there be a current induced in the coil if the magnet is rotated about its axis? Discuss.

How can we find the direction of the magnetic field due to a straight current-carrying conductor?