1. WALT – Explain how resistance is used in everyday life
Resistance is Useful!!!
WALT – Explain how resistance is used in everyday life

2. Resistance
The resistance of an electrical component is a measure of its opposition to current.
The two main ways of increasing the current in an electrical circuit are by increasing the voltage or by decreasing the resistance.

4. Can YOU think of ways in which we use resistors in the house?

5. (a) Changing the voltage
If you increase the voltage across a component, there will be more current through the component. Too high a voltage and the bulb will blow (diagram 3).

6. (b) Changing the resistance
If you increase the number of lamps in a series circuit, there will be less current. The lamps resist the current, so if you put more lamps into the circuit, there is more resistance.

7. You could do the same with a variable resistor.

8. The quantities voltage, current and resistance are linked by the relationship:
The symbol for resistance is R, it is measured in ohms (Ω)
The symbol for voltage is V, it is measured in volts (V)
The symbol for current is I, it is measured in amperes (A)

9. A torch lamp takes a current of 0. 3 amperes from a 3 volt battery
A torch lamp takes a current of 0.3 amperes from a 3 volt battery. Calculate its resistance. Can you work out the answer?

10. To calculate the resistance you need to take the following steps:
resistance = voltage/current
R = V/I = 3/0.3 = 10 ohms (10 Ω)
Answer: R = 10 ohms

11. Did you use the correct relationship?
Did you substitute values correctly?
Did you put the correct unit in your final answer?
Well done!

12. Place the Variable resistor in the following circuits and measure the current (A) as you vary the resistance

13. measuring current A A This is how we draw an ammeter in a circuit.
PARALLEL CIRCUIT
SERIES CIRCUIT

14. measuring voltage V V This is how we draw a voltmeter in a circuit.
SERIES CIRCUIT
PARALLEL CIRCUIT