Introduction to S grade electricity: S3 Current flow, circuit diagrams, measuring current

1. Electricity
3E: Wednesday 16th November

2. Electricity
• What is happening in the circuit?
• Circuit diagrams
• Measuring current

3. Model of current flow
Bakery
Supermarket
1. Bakery Manager loads
bread onto the vans and
sends them off
2. As soon as the vans start
to move, bread is delivered
to the supermarket.
3. All the vans
move at the
same speed.
4. If the manager speeds the vans up, more bread is delivered to the supermarket in a certain time.
5. If the manager loads more bread on each van, more bread is delivered to the supermarket in a certain
time.
The vans deliver the bread
to the supermarket where
the shoppers take it away.
The empty vans go
back to the bakery to
get more bread.
Each van takes bread to
the supermarket.
Empty vans collect
bread at the bakery.

4. Model of current flow
1. The battery provides
energy and makes the
charges move.
2. As soon as the charges
start to move, energy is
delivered to the bulb
3. All the charges
move at the
same speed
4. If the charges speed up, more energy is delivered to the bulb in a certain time.
5. If more energy is carried by each charge, more energy is delivered to the bulb in a certain time.
Charges deliver energy
to the bulb where it is
transferred to heat and
light.
Charges return to the
battery to collect more
energy.
Charges are atom sized
particles already in the
wire. The charges carry
energy.
Charges collect
energy at the battery.
The electric current
(Amperes) is the number
of charges passing a point
each second

5. Circuit diagrams
• Charges flow in a complete circuit
• Components in circuits are drawn using
symbols:

6. Measuring current
• Current (flow of charge) has symbol I, and is
measured in Amperes or Amps (A) for short
• We use an Ammeter to measure current
through a circuit