Question

1. which of these materials is a good conductor?

a) rubber
b) glass
c) copper
d) wood

1. what happens to the resistance of a wire if its length is doubled?

a) halved
b) doubled
c) quadrupled
d) unchanged

1. what is measured in volts?

a) resistance
b) current
c) voltage
d) charge

1. magnetic field lines outside a magnet go from

a) north to south
b) south to north
c) both directions
d) inside the magnet only

1. what type of magnet is earth?

a) electromagnet
b) permanent magnet
c) temporary magnet
d) none of these

Explanation:

• For question 5, copper is a metal and metals are good conductors while rubber, glass and wood are insulators.
• For question 6, resistance of a wire is directly proportional to its length (using the formula $R =

ho\frac{l}{A}$, where $R$ is resistance, $
ho$ is resistivity, $l$ is length and $A$ is cross - sectional area), so if length is doubled, resistance is doubled.

• For question 7, voltage is measured in volts. Resistance is in ohms, current in amperes and charge in coulombs.
• For question 8, magnetic field lines outside a magnet go from north to south.
• For question 9, Earth is considered a permanent magnet due to its magnetic field generated by the molten iron - nickel core in its interior.

Answer:

1. c) Copper
2. b) Doubled
3. c) Voltage
4. a) North to South
5. b) Permanent magnet