P6 FlavourSharing

Charging

Logic gates

Motoring and Generators

Resist

ing

Computer circuits

Tran

sform

e

rs

16 -18 lessons8 Home worksEnd of topic assessment

P6 – Electricity for Gadgets

Lesson 1 – Resistance

Learning aim: Demonstrate an understanding of variable resistance and ohmic conductors

Learning Objectives Success Criteria

Recognise electrical symbols.

Understand electrical resistance of an ohmic conductor and how it can be varied.

Calculate resistance and interpret voltage–current graphs.

Recognise and draw circuit symbols (Grade E-D)

Use the equation resistance = voltage / current to calculate resistance (Grade C)

Describe and explain how a variable resistor (rheostat) can be used to vary the brightness of a lamp. (Grade C-A)

Draw and interpret voltage–current graphs for ohmic conductors. (Grade C-A)

Use a textbook or other resource to fill in the table below:

Component Circuit symbol

Fuse

Switch

Resistor

Motor M

Component Circuit symbol

Cell

Voltmeter

Battery

Ammeter A

V

Use a textbook or other resource to fill in the table below:

Current and Charge

An electric current is the flow of charge carrying electrons.

Current is measured in amps with an ammeter connected in series.

Charge is measured in coulombs

Q

tIQ = Charge (coulombs – C)I = Current (amps – A)T = Time (seconds – s)

Investigating current and voltage

Georg Simon Ohm 1789-1854

ResistanceResistance is anything that will

RESIST a current. It is measured in Ohms, a unit

named after me.

The resistance of a component can

be calculated using Ohm’s Law:Resistance = Voltage

(in V)

(in ) Current (in A)

V

RI

A filament bulb has a current of 20 A running through it, with a potential difference of 100 V across it.

What is the resistance of the filament in the bulb?

V = IR

R = V I

= 100 V 20 A= 5

Calculating the resistance of a bulb

Resistance calculations

Plenary - Matching sentences

1. Electric current is measured in… a. …the brighter the light.

2. A battery is… b. …the voltage across it is decreased.

3. The ohm is… c. …several cells connected in series.

4. The greater the current in a circuit containing a lamp… d. …the rate of flow of electric charge.

5. If the resistance in a circuit is increased… e. …amperes.

6. If the resistance of a resistor is decreased…

f. …using a voltmeter connected in parallel with it.

7. The voltage across a resistor is measured… g. …the unit of resistance.

8. An electric current is… A. …the current is smaller.

Resistance is anything that opposes an electric current.

Resistance (Ohms, ) = Potential Difference (volts, V)

Current (amps, A)What is the resistance of the following:

1) A bulb with a voltage of 3V and a current of 1A.

2) A resistor with a voltage of 12V and a current of 3A

3) A diode with a voltage of 240V and a current of 40A

4) A thermistor with a current of 0.5A and a voltage of 10V

Learning Objectives Success Criteria

Recognise electrical symbols.

Understand electrical resistance of an ohmic conductor and how it can be varied.

Calculate resistance and interpret voltage–current graphs.

Recognise and draw circuit symbols (Grade E-D)

Use the equation resistance = voltage / current to calculate resistance (Grade C)

Describe and explain how a variable resistor (rheostat) can be used to vary the brightness of a lamp. (Grade C-A)

Draw and interpret voltage–current graphs for ohmic conductors. (Grade C-A)