## Electricity

1. Calculate the length of a copper wire of cross sectional area 0.8x10-7m2 that has a resistance of 2Ω.

2. Calculate the resistivity of a material if a 2.5 m length of wire of that material with a diameter of 0.3 mm has a resistance of 3Ω

3. Calculate the resistance between the large faces of a slab of germanium of thickness 1 mm and area 1.5 cm2.

4. Calculate the length of a eureka wire of diameter 0.8 mm that has a resistance of 8Ω

5. Calculate the current flowing in a copper wire of cross-sectional area 3x10-7m2 if the drift velocity is 0.2mms-1.

6. Calculate the drift velocity in a silver wire of cross-sectional area 1.5x10-7m2 if a current of 25mA flows through it.

7. Calculate the current through the following resistors:
(a) 120Ω connected to 240V
(b) 4700 Ω connected to 12V
(c) 10kΩ connected to 6V
(d) 2.5MΩ connected to 25V

8. What is the resistance of the following?
(a) a lamp that draws 2A from a 12V supply
(b) a kettle that draws 4A from a 240V supply

9. The two lines on the graph in the diagram show a specimen of metal wire at two different temperatures.
(a) calculate the resistance of the wire at each temperature
(b) which line shows the higher temperature?