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**1. ****Describe an experiment to determine the resistance of a resistor.**

- Set up the apparatus as show in the diagram above.
- Adjust the rheostat to the maximum so that the smallest possible current flows in the circuit.
- Record the ammeter reading (I) and the voltmeter reading (V).
- Adjust the rheostat to allow a larger current to flow in the circuit. Record the values of I and V.
- Repeat the procedure to obtain five sets of I and V readings.
- Plot a graph of V against I. Draw a best fit line.
- The gradient of the graph gives the resistance of the resistor.

**2. ****Define Ohm’s law.**

- Ohm’s law states that for metallic conductor, the current passing through it is directly proportional to the potential difference provided physical conditions such as the temperature remains constant

**3. ****Explain why the component with a voltage-current graph as shown below obeys Ohm’s law (is an ohmic conductor).**

- For an Ohmic conductor, the current passing through it is directly proportional to the potential difference provided that the temperature remains constant.
- The graph shown is a straight line through the origin which indicates that V is directly proportional to I.

**4. ****Draw the voltage versus current graph of a filament lamp and explain why Ohm’s law does not apply to the filament lamp. Give a reason for the relationship.**

- The graph is a curve which indicates that V is not directly proportional to I. Therefore, it does not obey Ohm’s Law.
- When the current flows through the filament, its temperature increases. This causes its resistance to increase.