KS3 SCIENCE : ELECTRICITY 2

1
KS3 SCIENCE ELECTRICITY 2

• By the end of this lesson you should be able to..
  
• Recall that ammeters are used to measure the
  size of a current in a circuit, and should be
  always connected in series.
• Use it in practical circuits and recall that
  current is measured in amperes (A).

2
Current in series circuits

• Electrons are real particles. When they move
  through a bulb (or any other electrical device)
  they do not disappear! They simply use up some
  (or all) of the electrical energy they got from
  the cell.
• Do you think the speed of the electrons are
  different at different points in a series
  circuit?
• We can use an AMMETER, which measures the size of
  the current , to find out.

3
Look at the paragraph below. Write down words to
fill in the gaps. Guess if you have to, and use
as many words as you want in each space!

• In any circuit the free electrons __________ in
  the same __________ when pushed by a _________
  supply. The bigger the voltage, the more
  _________ the electrons have, and the _________
  they will flow. If this happens more _________
  will be delivered to the bulb per second and it
  will be ________. For any electron to move
  forward, a space must be created for it to move
  into. So they must all move in time. I think that
  the speed at which the ________ drift along will
  _________ after going through a bulb. I will be
  able to tell that this has happened since the
  reading on the ammeter will ________.

4
Set up the circuit shown and test it to ensure
that the bulb works.Use the switch on the power
pack to switch the circuit on or off.
MEASURING THE CURRENT IN A CIRCUIT
Now switch off the power and connect an ammeter
so that you can record the current going into and
out of the bulb. After taking readings, turn the
voltage down slowly and record your observations
5
Re-evaluate your initial statement then click to
see the answers

• In any circuit the free electrons __________ in
  the same __________ when pushed by a _________
  supply. The bigger the voltage, the more
  _________ the electrons have, and the _________
  they will flow. For any electron to move forward,
  a space must be created for it to move into. So
  they must all move in time. I think that the
  speed at which the ________ drift along will
  _________ after going through a bulb. I will be
  able to tell that this is true since the reading
  on the ammeter will
• ________.

flow
direction
power
energy
faster
electrons
be the same
be the same
6
Set up the circuit shown and test it to ensure
that it works.
SERIES CIRCUITS (2)
You now need to turn it off, and insert an
ammeter to measure the current at the positions
marked with an X. Connect your ammeter in series,
and record the reading in amperes (A).
7
Use your readings from the second circuit to fill
in the blanks. Click again to see the answers

• When two bulbs are connected in ______ it becomes
  more difficult for the electrons to ____ through
  the circuit. They will flow slower than if there
  was ______________ in the circuit. As a result,
  the current will ________ and the bulbs will be
  ______ since they are getting less ______
  delivered to them per ______. The total energy
  provided by the __________ will be ______________
  the two bulbs.

series
flow
only one bulb
dimmer
decrease
energy
second
power pack
shared between
8
Use this website to simulate these experiments
and double check what you have found. Click on
the circuit construction kit.