The major problem in harnessing nuclear energy is how to

Why is a biogas plant a safe and efficient method of waste disposal? Justify.

Give two uses of coke.

"$A$ biogas plant solves the fuel as well as environmental problems". Discuss.

For producing electricity,the energy from flowing water is preferred to energy obtained by burning coke. State two reasons for it.

$(a)$ Magnetic field lines of two bar magnets $A$ and $B$ are as shown below. Name the poles of the magnets facing each other.
$(b)$ Two magnetic field lines never intersect each other. Why?
$(c)$ How does the strength of the magnetic field at the centre of a current-carrying circular coil depend on the
$(i)$ radius of the coil,
$(ii)$ number of turns in the coil, and
$(iii)$ strength of the current flowing in the coil?