6. A circular coil with a radius of 50 mm consists of 280 turns of wire. The current in the wire is 16 mA. What is the magnetic field strength at the centre of the coil? (Permittivity of free space is 8.86 x 10-12) [ a) 5.415 x 10-5T [ b) 5.630x 10-5T [ c) 5.415 x 10-4T [d) 5.415x10 4T 7. An electric heater is operated by applying a potential di"erence of 50.0 V to nichrome wire of resistance 8.0 0. What is the current carried by the wire? [ a) 5.0 A [ b) 5.25A [ c) 6.25 A [ d) 6.7A 8. The capacitor within a flash unit of a camera has a capacitance of 5 F. What is the charge on the capacitor when it is charged to 6.0V? [ a) 0.83 C [ b) 1.2 C c) 15 JC [ d) 30 uC 9. The maximum current of circuit is 20.0 A at an operating voltage of 1.20 x 102 V. How many 75 W bulbs can be operated with this voltage source? [ a) 12 [ b) 22 [ c) 32 [ d) 42 10. The force on a 2.5 uC charge in an electric field is 3.0 x 10-5 N. What is the magnitude of the electric field? [ a) 1.2 NC-1 [ b) 12 N C-1 [c) 0.69 NC-1 [ d) 7.5 x 10-11 N C-1