Download Modelling Electricity

Task : Copy and fill in the blanks
Electrons are ………….. charged sub-atomic particles. They move
around the circuit through ……………. materials such as metal
wires.
A cell has a positive and negative side. The ……….. flow out of the
negative side and ……….. the positive side. This is called the electron
flow.
electrons
negatively
towards
conductive
Modelling Electricity
 To be able to use a model to explain current and voltage in electrical circuits
Symbols
 Look at the following symbols for components – can you name them all?
Cell
Resistor
Bulb
Switch
Battery
Buzzer
Fuse
Voltmeter
Ammeter
Motor
Variable Resistor
Key Terms
 What is current, voltage and resistance?
 Current – the flow of electrons around the circuit
 Voltage – driving force which pushes the current around
 Resistance – anything in the circuit which slows the flow down
Task 2: Voltage and current = the electrical
energy
voltage
Voltage is a measure of
the energy carried
Voltage is used up in
components
Voltage is measured in volts, V
Voltage is measured with a voltmeter
Current
Current is the rate of flow
Current is not used up,
what flows into a component
must flow out.
Current is measured in amps
(amperes), A
Current is measured with an ammeter
Series Circuits
 What are series circuits?
 Series circuits are ‘all or nothing’ – the different components are connected in a
line, end to end
 Disconnecting one component breaks the circuit, meaning all the components
stop
 The same current flows through all parts of the
+
A
-
circuit
 The size of the current depends on the voltage and
resistance (I = V/R)
 The total voltage is shared between the components
- the bigger the resistance of a component the bigger
its share of the voltage
Series Circuits
6V
0.5A
A
1.5V
-
+
3Ω
5Ω
2.5V
4Ω
2V
 Voltages add to equal the supply: 1.5V + 2V + 2.5V = 6V
 Total resistance is the resistance of all the components: 3Ω + 4Ω + 5Ω = 12Ω
 Current = voltage ÷ resistance: 6 ÷ 12 = 0.5A
Parallel Circuits
 What are parallel circuits?
 In parallel circuits each component is separately connected to the +ve and –ve
of the supply
 Removing one component barely affects the others
 All components get the full voltage
 The current through each component depends on its
branch 1
branch 2
resistance – the lower the resistance the more
current that flows through
 The total current flowing around the circuit is equal
to the total of all the currents in the separate
branches
Parallel Circuits
+
6V
A1
5.5A
4Ω
A2
6V
1.5A
2Ω
A3
6V
3A
6Ω
A4
1A
6V
 Voltages are all equal to the supply: 6V
 Total resistance is less than the smallest resistance: <2Ω
 Current (A1) equals the sum of all the branches: A2 + A3 + A4 etc… (5.5A)
Assessment
 Complete the circuits worksheet
Assessment
E, F, T, J, or L
2.
A, B, C, D, G, H, or K
3.
A and I
4.
Add some more cells (>2 cells = a battery)
5.
B
6.
B, D, G, H, or K (2 of these)
7.
A or C
8.
The switch is open
9.
B, D or K
10. F
1.
Assessment
11.
V
V
12.
B, D or K
Assessment
13.
6A – the current should split evenly down each branch if the resistance of the
components in each branch is equal
15. 2.5V – the voltage is shared between all the components in a series circuit
14.