Download Chapter 19: Electric Charges and Currents

Chapter 19:
Electric Charges and Currents
19-4 and 19-5:
Electric Circuits and Electric Power
Electric Circuits
• An electric circuit provides a complete,
closed path for an electric current.
• An electric circuit consists of a source of
energy (voltage source), a load
(resistance), wires, and a switch
Electric Circuits
• Source: battery, thermocouple, etc.
• Load: uses electric energy (light bulb, appliance, etc.)
- offers some resistance to current flow
• Switch: opens and closes the circuit
• A current needs a closed path - if a switch is
off, the circuit is open.
Parts of an Electric Circuit
Source (Battery)
Load (Light Bulb)
Electric Circuits
• Electricity cannot flow through an open circuit.
Electricity can only flow through a closed
circuit.
Closed Circuit
Open Circuit
Series and Parallel Circuits
• Series Circuit: circuit in which all parts are
connected one after another. If there is a break,
the entire circuit is opened and no current flows
• Parallel Circuit: circuit in which different parts
are on separate branches. If there is a break,
electrons can still move.
Series and Parallel Circuits
Series Circuit
Parallel Circuit
Series and Parallel Circuits
• Fuse: this strip of metal
used for safety because
when the current flowing
through it becomes too
high, it melts and breaks
the flow of electricity
- Protects against too
much current flow
(overload)
- Once fuses burn out
they must be replaced
Series and Parallel Circuits
• Circuit Breaker: reusable device that protects a circuit
from being overloaded
- Easier to use than fuses
Electric Power
• Electric Power is the ratio at which electric
energy is used by doing work, or by changing to
a different form, such as heat or light
Power = Voltage x Current
P=VxI
Watts = Volts x Amperes
Electric Energy
Energy = Power x Time
E=Pxt
Kilowatt-hours = Kilowatts x hours