Download P5 – Electrical Circuits

P5 – Electrical Circuits
Electrostatics can be shocking.
Electrostatics can be annoying – or even dangerous.
Electrostatics can be annoying – or even dangerous.
Electrostatics can be annoying – or even dangerous.
Electrostatics can be useful.
What is the difference?
• What is the difference between a series and parallel circuit?
• Which is which?
What is the difference?
• Series circuit
– The electrical current needs to pass through all of the components before it gets back to the battery
• Parallel circuits
– The electrical current does not have to go through all of the components, the circuit has different branches Current Rules
• Current is the same everywhere in a series circuit.
• Current splits at the branches in parallel circuits, this depends on the resistance of each branch. Higher resistance = lower current.
Resistance
• The more resistance there is the less current is able to flow. Therefore more resistance causes less current.
• Resistance (Ω) = Voltage (V)
Current (A)
Make the equation triangle for this equation
A way of picturing what a resistor does
What causes the current in this circuit?
• The battery.
But, what is it that actually makes the charges move?
• The chemical reactions inside the battery cause a difference of some kind between the terminals of the battery.
Here, a height difference (a difference in gravitational potential energy) causes the ball to move.
Rules
Current
• Series – The current is the same in all parts of a series circuit
• Parallel – The current splits at the joins depending on the resistance of the components on each path
Rules
Resistance
• Series – The resistance is added together
• Parallel – The resistance decreases as there are additional paths for the current
Rules
Voltage
• Series – The sum of the voltage of each component is equal to the voltage supplied by the power supply
• Parallel – The voltage of each split is the same as supplied by the supply.
Light dependant resistor (LDR)
As light intensity increases, resistance ………… The relationship is not linear.
Thermistor (Temperature dependant)
Electrical Power
• Every device uses a different amount of electrical power. This gives them their rating in Watts. • This is calculated as their voltage x the current they use:
– Power (W) = Voltage (V) x Current (A)
– P = VI
Electrical Energy
• Everything converts this electrical power into energy depending on the duration of time that it is left on.
• Energy (J) = Power (W) x Time (s)
• E = Pt
• Energy (kWh) = Power (kW) x time (h)
Why kWh and not joule?
• How many joules in a kWh?
• Energy = Power x time
kWh = 1000W x (60x60)
1kWh = 3 600 000J
• So why do we use kWhs to calculate your household energy usage and not joules?
Generating Electricity
• There are three important points when considering generating electricity:
– Movement
– Electric Current – Magnetism
• If you have two of these you can create the third.
Generator
Increasing Output
1. Add an iron core
2. Increase the number of turns
3. Increase the speed of rotation
Power Station
Transformers
National Grid
• The national grid uses step up transformers to increase the voltage, which decreases the current.
• This reduces the lose of energy due to heat/friction in the cables.
• The voltage is then stepped down at a local level to be safe when people use it.