Household circuits and power

Household

circuits and power

Direct vs Alternating Current

Alternating Current

-From the power
company

-Electrons switch
directions

Direct Current

-From a battery

-Electrons flow in
one direction

AC is easier to
transmit over long
distances

In the US:

-Electrons
change
directions
60x/sec (60
Hz)

-Voltage coming
into the house
is 120 V

Fuses and Circuit Breakers

Prevent high CURRENTS in
circuits which could lead to a fire

● High currents could be caused

by:
○ A short circuit
○ Two many appliances

turned on in one circuit

Fuses and Circuit Breakers

Fuses - a metal piece inside melts if the
current gets too high - fuse must be
replaced

Circuit breaker - switch is triggered to flip
if the current gets too high - can just be
reset by flipping the switch back

Symbol for fuse in a circuit

Multiple Choice

The type of current where charges flow in one direction

• Direct Current

• Alternating Current

• Electron Flow

• Voltage

Multiple Choice

A(n) ______________ is a reusable safety switch that breaks the circuit when the current gets too high.

• Fuse

• Grounded wire

• Fuse box

• Circuit breaker

Multiple Choice

A device that contains a thin strip of metal that melts easily if the current in the circuit is too high

• Fuses

• Circuit

• Series circuit

• Circuit breaker

Multiple Choice

The type of current where charges shake back and forth in a circuit

• Alternating Current

• Direct Current

• Voltage 

• Switchback Current

Power in Circuits

The rate at which electrical energy is converted at an
element in a circuit.

Related to the voltage and the current in a circuit

Work – Joules

Power - Watts

Power practice

1.

How much power is used by a cell phone charger plugged into the
wall with 120V if 0.5A of current pass through it?

2.

20 watts of power is produced in a circuit with 0.2 amps of current
flowing. What is the voltage in the circuit?

P =
I =
V =

P =
I =
V =

Power practice

1.

How much power is used by a cell phone charger plugged into the
wall with 120V if 0.5A of current pass through it?

2.

20 watts of power is produced in a circuit with 0.2 amps of current
flowing. What is the voltage in the circuit?

P = ?
I = 0.5 A
V = 120 V

P = 20 watts
I = 0.2 A
V = ?

P = (0.5)(120)
P = 60 Watts

20 = (0.2)(V)
V = 100 Volts

Multiple Choice

What is the unit of Electrical Power?

• Joule

• Watt

• Where

• Amp

Multiple Choice

Calculate the voltage applied when a 60 watt light-bulb uses a current of 5 amps

• 300 volts

• 30 volts

• 12 volts

• 0.08 volts

Multiple Choice

What is the power of a 20V bulb with 5A through it?

• 100W

• 100V

• 6.3W

• 6.3A