3️⃣ PAG6 - investigate resistance of metallic wires

Question 1

Equipment

Answer 1

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Question 2

Aim

Answer 2

The aim of this experiment is to investigate how the length of a wire at a constant temperature affects the resistance of electrical circuits

Question 3

Method

Answer 3

• Set up the apparatus by connecting two crocodile clips to the thin resistance wire a distance of 10 cm apart and setting the power supply to 1.5 V
• Connect the wire, using the clips, to the rest of the circuit
• Record the potential difference from the voltmeter and current from the ammeter
• Move the clips in 10 cm intervals further apart
• Take new measurements from the voltmeter and ammeter for each length reading
• Continue until the crocodile clips are a length of 1 m apart

Question 4

Analysis of results?

Answer 4

Calculate the resistance of each length of wire using the equation:
Resistance Equation
Where:
R = resistance (Ω)
V = potential difference (V)
I = current (A)
Plot a graph of resistance (on the y-axis) against length (on the x-axis) and draw a line of best fit

The graph should be a straight line through the origin with a positive correlation
This means that the longer the piece of wire, the higher the resistance
In other words, the resistance is directly proportional to the length of the wire

Question 5

Juystifaction for results

Answer 5

The greater the length of wire the greater the number of collisions between the free electrons and metal ions.

This will result in greater resistance.

Question 6

Errors

Answer 6

The temperature of the wire must be kept constant.

Whenever a current flows through a conductor there is a heating effect.

Electrical energy is converted to heat energy.

To ensure the temperature of the wire does not increase, switch off between readings and keep the current as low as possible.

Read the ammeter and voltmeter accurately by reading the scale from directly above the pointer or use digital instruments.