A circular coil of radius $$R$$ has a resistance of $$40 \Omega$$. Figure shows two points $$P$$ and $$Q$$ on the circumference separated by a distance $$\frac{\pi R}{2}$$ which are connected to a 16 V battery with internal resistance of $$0.5 \Omega$$. What is the value of current $$I$$ flowing through the circuit?

An $$\alpha$$-particle of energy 10 eV is moving in a circular path in uniform magnetic field. The energy of proton moving in the same path and same magnetic field will be [mass of $$\alpha$$-particle $$=4$$ times mass of proton]

In communication system, a repeater is used to extend the range to transmission. It is the combination of

Two wires of different materials have same length $$L$$ and same diameter $$d$$. The second wire is connected at the end of the first wire and forms one single wire of double the length. This wire is subjected to stretching force $$F$$ to produce the elongation I. The two wires have