Investigating how length of wire affect current flowing in circuit

 

To investigate how changing the length of a resistance wire affects the current flowing through an electrical circuit.

Hypothesis:

As the length of the wire increases, the current decreases because a longer wire has greater electrical resistance.

Variables:

• Independent variable: Length of the wire (cm)

• Dependent variable: Current (A)

• Controlled variables: Potential difference, material and thickness of wire, temperature, and other circuit components.

Apparatus:

Battery/power supply, resistance wire (e.g. nichrome), ammeter, voltmeter, switch, connecting wires, and metre ruler.

Method:

1. Set up a circuit containing the power supply, ammeter, voltmeter and resistance wire in series.

2. Place the resistance wire alongside a metre ruler.

3. Connect a resistance wire at 20 cm and record the current and voltage.

4. Repeat for wire lengths of 30 

6. Repeat each reading three times and calculate the mean current.

7. Switch off the circuit between readings to prevent the wire from heating up.

Expected Result:

As the length of the wire increases, its resistance increases and the current decreases.

Scientific Explanation:

A longer wire provides a longer path for electrons. The electrons experience more collisions with the ions in the wire, increasing resistance. According to Ohm’s law, I = V/R, when voltage is constant, an increase in resistance results in a decrease in current.