ELECTRIC Circuits

1
ELECTRIC Circuits
2
CIRCUITS

• A circuit is a closed, continuous path through
  which electricity flows.

3
Power

• Moving charges in an electric circuit can do
  work.
• The rate of doing this work is called electric
  power.
• Power current x voltage.

4
CIRCUITS

• Just like water flowing in a closed pipe,
  electricity flows in a closed circuit.
• If the circuit breaks, electricity no longer
  flows, just like water wouldnt flow in a broken
  pipe.

5
Check Your Neighbor

• Which draws more current, a 40-W bulb or a 100-W
  bulb?

6
Check Your Neighbor

• What power is needed to operate a clock radio if
  it draws a current of 0.05 A from your household
  circuit? (HINT What is the voltage in a
  household circuit?)

7
CIRCUITS

• Circuits typically include a voltage source such
  as a battery or outlet, a conductor such as a
  wire, and one or more resistors.

8
CIRCUITS

• There are 2 main types of electrical circuits
• Series circuits provide only one loop through
  which current can flow.
• Flashlights and some Christmas lights are series
  circuits.

9
CIRCUITS

• Parallel circuits provide 2 or more paths through
  which current can flow.
• Your home is wired in parallel.

10
SERIES CIRCUIT

• Because the parts of a series circuit are wired
  one after another, the amount of current is the
  same through all parts.

11
SERIES CIRCUIT

• If one light bulb blows in a series circuit, they
  all go out, because the circuit has been opened
  (or broken).

12
SERIES CIRCUIT

• The current is resisted by the resistance of the
  first device, the resistance of the second
  device, etc. So the total resistance in the
  circuit is the sum of the individual resistances.

13
Check Your Neighbor

• What happens to the current in other light bulbs
  in a series circuit if one bulb burns out?
• What happens to the light intensity of each light
  bulb in a series circuit when more bulbs are
  added to the circuit?

14
PARALLEL CIRCUIT

• In a parallel circuit, the current splits up to
  flow through different branches.

15
Check Your Neighbor

• In a circuit consisting of 2 lamps connected in
  series, if the current through 1 lamp is 1 A,
  what is the current through the other lamp?

16
PARALLEL CIRCUIT

• A break in any one path does not interrupt the
  flow of charge in the other paths, so they remain
  lit.

17
PARALLEL CIRCUIT

• Because all branches connect to the battery or
  outlet, they all receive the same voltage.
• However, branches with lower resistance receive
  more current.

18
Parallel Circuit

• Each branch can have its own resistance, so the
  current varies in each branch also.
• As the number of branches increases, the
  resistance in the circuit decreases.

19
Parallel Circuits

• As more devices are connected to the circuit, the
  resistance lowers, and the current increases.
  This can lead to the circuit being overloaded
  with more current than is safe.

20
Check Your Neighbor

• In a circuit consisting of 2 lamps connected in
  parallel, if there is 6 V across one lamp, what
  is the voltage across the other lamp?

21
Parallel Circuits

• To prevent overloading, circuits contain fuses or
  circuit breakers.
• When too much current flows through a wire, the
  fuse or circuit breaker turns off the current in
  that wire, thus preventing electric shock or fire.