The magnetic field around a current-carrying straight conductor is:

$A$ fuse is a $.......$ wire.

All the distribution circuits for domestic purposes are parallel connections.

$(i)$ $A$ compass needle gets deflected when brought near a current-carrying conductor. Why?
$(ii)$ What happens to the deflection of the needle when the current in the conductor is increased?

$(a)$ 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?

$A$ 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.