Question 11

(a)        State two uses of electromagnets.
(b)       A resistance wire has a length of 1.5 m and cross-sectional area of 7.85 x 10-7m2. If the wire is connected across the left gap of a metre bridge and a 5 Ω resistor across the right gap, a balance point of 60.0 cm from the left side of the bridge wire is obtained. Calculate the resistivity of the wire.
(c)       The plates of a parallel plate capacitor each of are 2.0 m2 are 5.0 x 10-3m apart in air. If the p.d. across the plates is 10 kV, calculate the:
(i )  capacitance of the capacitor;
(ii)  charge on each plate;
(iii) electric field intensity across the places.

(d) (i)  Define electrical potential at a point in an electric field.
      (ii) State the relationship between electric potential, V and electric field intensity,E.