An isolated metal sphere of radius R, carrying an electric charge Q, is situated in the medium of relative permitivity, E_r. A test charge is placed at a point p, distance r from the surface of the sphere. Let E_o represent the permitivity of free space. The magnitude of the electric field intensity at P is given by the expression

A resistor of resistance R is connected to a battery of negligible internal resistance. If a siilar resistor is connected in series with it the

A cell of e.m.f. 1.5V is connected in series with a resistor of resistance 3.0\(\Omega\). A voltmeter connected across the cell registers 0.9V. Calculate the internal resistance of the cell

A wire of resistivity 4.40 x 10^-5\(\Omega\) cm has a cross sectional area of 7.50 x 10^-4 cm². Calculate the length of the wire that will be required to make a 4.0\(\Omega\) resistor