Ohm’s Law – The relationship between Current, Voltage and Resistance.

Starter Decode the information from the sheet. Write the solution in your book.

Solution - Resistance Electrons carry current around a circuit. Sometimes the electrons collide with the atoms that the wire is made out of. This is what causes resistance. There are more collisions in a long wire than a short wire and more in a thin wire than a thick one. This means the wire with the least resistance is a short thick one.

Ohm’s Law Today we’re going to investigate the relationship between current and voltage. We will carry out a practical where we will change the voltage of our power supply and measure the resulting change in current.

Make a prediction! Write the title “Investigating Ohm’s Law” in your book…this is a lab report! Make a sub-heading “Prediction” Under this you need to make your own prediction – what do you think will happen in the experiment? How do you think the current will change as we increase the voltage?

Equipment list Make a new sub-heading “Equipment list” Make a list using bullet-points of the equipment we will use: Power supply Connecting wires 1 bulb 1 variable resistor 2 multimeters 1 switch Write a short note to describe what each piece of equipment is used for.

Circuit diagram Make a sub-heading “Circuit Diagram” Draw a circuit diagram: 5 – 7 V A V

Procedure Make a sub-heading “Procedure” Set up the circuit as it is in the circuit diagram without the meters. The switch should be open and voltage set to zero. Add a multimeter in series to act as an ammeter. Set it to the 10 A setting using the “COM” and “10A” connections. Set the other multimeter to the 20 V setting. Plug connecting wires into “COM” and “V Ω mA” and connect it in parallel across the bulb. Close the switch and increase the voltage to 5 V Record the current value. Repeat the experiment increasing the voltage each time by 0.5 V until you reach 7 V Repeat the full experiment.

Results Table – Make a sub-heading!!  Voltage (V) Test 1 (A) Test 2 (A) Average Current (A) 5.00 5.50 6.00 6.50 7.00

Results Table – Make a sub-heading!!  Voltage (V) Test 1 (mA) Test 2 (mA) Average Current (mA) 0.50 22 18 1.00 40 1.50 59 61 2.00 81 79 2.50 100 3.00 122 118

Make a sub-heading “Graph” We will plot a graph with “Voltage (V)” on the x- axis and “Average Current (A)” on the y-axis.