what is electricity? electricity is the flow of moving electrons. when the electrons flow it is...
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What is Electricity?Electricity is the flow of moving electrons. When the electrons
flow it is called an electrical current.
Electric CurrentElectric current is the rate at which charges pass a given point.
When the current is high, more charges pass the point each second.
Electric Current
•Symbol of current in formula: I•Units: amperes or amps
•Symbol of amperes or amps: A
VoltageVoltage is the potential difference between two
points in a circuit.Voltage is the potential energy that makes the
electrical current flow in a circuit by pushing the electrons around.
Voltage• A measure of how much work is needed to move a charge
between two points.
• The size of the current depends on the voltage. If the voltage between two points on a wire is increased, more current will flow in the wire.
Conductors and insulators
• A conductor in electricity is a material that allows electrons to flow through it easily. Metals, in general, are good conductors. • An insulator is a material that is a poor conductor of electricity.
Examples include plastic, wood, ceramic and glass.
Conductance
• Symbol of conductance in formula: G• Units: Siemens• Symbol of ohms: S
• To calculate conductance in terms of Resistance, we use this formula:R= 1/G G= 1/R
Exercises1. What current flows between a potential difference of 120 V
through a resistance of 30 Ω?2. A motor with an operating resistance of 30 Ω is connected to
a voltage source. 4.0 A of current flow in the circuit. What is the voltage of the source?
3. If the conductance of a circuit is 0.25 S, and the current is 2.0 A, what is the overall voltage?
4. An ammeter measures current. What will the ammeter read when it is connected to a 90 V source and a 60 Ω resistor?
Electrical Power
• The rate at which electrical energy is changed into other forms of energy. The watt tells how quickly a device (e.g. bulb) uses electrical energy.
• Symbol of power in formula: P• Units: watts (Joules/s)• Symbol of watts: W
Power= voltage x current
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