$A$ square coil moves in a plane with uniform velocity $v$ parallel to its sides. $A$ magnetic field $B$ points perpendicular and into the loop. What is the induced current in the coil?

$(a)$ An electric current is passed in a horizontal copper wire from east to west. Explain your observations when a compass needle is placed $(i)$ below this wire,$(ii)$ above the wire. Draw inference from your observations.
$(b)$ List the factors on which the strength of the magnetic field due to a straight conductor carrying current depend. How should these be changed to decrease magnetic field at a point?

Why are magnetic field lines closed curves?

$(a)$ What is the function of an earth wire in electrical instruments? Why is it necessary to earth the metallic electric appliances?
$(b)$ Explain what is short-circuiting and overloading in an electric supply.
$(c)$ What is the usual capacity of the fuse wire in the line to feed:
$(i)$ lights and fans?
$(ii)$ appliances of $2 \,kW$ or more power?

$A$ device used for producing current is:

In the diagrams shown below:
$(i)$ Name the type of current in two cases.
$(ii)$ Identify any one source for each type of these currents.
$(iii)$ What is the frequency of current in case $(ii)$ in India?
$(iv)$ Use above graphs to write two differences between the current in two cases.