Are located on the outer edges of atoms…they can be moved .
A concentration of electrons in an atom creates a net negative charge.
If electrons are stripped away, the atom becomes positively charged.
The world is filled with electrical charges : + - + + + + + + + + + - - - - - - - - -
What is this electrical potential called?
- - - - - - - + + + + +
The build up of an electric charge on the surface of an object.
The charge builds up but does not flow.
Static electricity is potential energy . It does not move. It is stored .
Occurs when there is a loss of static electricity due to three possible things:
Friction - rubbing
Conduction – direct contact
Induction – through an electrical field (not direct contact)
Electricity that moves …
Current : The flow of electrons from one place to another.
Measured in amperes (amps)
How can we control currents?
With circuits .
Circuit : is a path for the flow of electrons. We use wires .
There are 2 types of currents:
Direct Current (DC) – Where electrons flow in the same direction in a wire.
There are 2 types of currents:
Alternating Current (AC) – electrons flow in different directions in a wire
simple circuits Here is a simple electric circuit. It has a cell, a lamp and a switch. To make the circuit, these components are connected together with metal connecting wires. cell lamp switch wires
simple circuits When the switch is closed, the lamp lights up. This is because there is a continuous path of metal for the electric current to flow around. If there were any breaks in the circuit, the current could not flow.
circuit diagram battery switch lamp wires Scientists usually draw electric circuits using symbols;
circuit diagrams In circuit diagrams components are represented by the following symbols; battery switch motor ammeter voltmeter resistor
types of circuit There are two types of electrical circuits; SERIES CIRCUITS PARALLEL CIRCUITS
The components are connected end-to-end, one after the other. They make a simple loop for the current to flow round. SERIES CIRCUITS If one bulb ‘blows’ it breaks the whole circuit and all the bulbs go out.
PARALLEL CIRCUITS The current has a choice of routes. The components are connected side by side. If one bulb ‘blows’ there is still be a complete circuit to the other bulb so it stays alight.
measuring current Electric current is measured in amps (A) using an ammeter connected in series in the circuit. A
measuring current This is how we draw an ammeter in a circuit. SERIES CIRCUIT PARALLEL CIRCUIT A A
measuring current SERIES CIRCUIT PARALLEL CIRCUIT
current is the same
at all points in the
2A 2A 2A
current is shared
2A 2A 1A 1A
Conductors vs. Insulators
Conductors – material through which electric current flows easily .
Insulators – materials through which electric current cannot move .
What is Resistance?
The opposition to the flow of an electric current, producing heat .
The greater the resistance, the less current gets through.
Good conductors have low resistance.
Measured in ohms.
What Influences Resistance?
Material of wire – aluminum and copper have low resistance
Thickness – the thicker the wire the lower the resistance
Length – shorter wire has lower resistance
Temperature – lower temperature has lower resistance
What is Voltage?
The measure of energy given to the charge flowing in a circuit.
The greater the voltage, the greater the force or “pressure” that drives the charge through the circuit.
Difference between Volts and Amps
Example – you could say that…
Amps measure how much water comes out of a hose.
Volts measure how hard the water comes out of a hose.
Ohm’s Law Ohm's Law defines the relationships between (P) power, (E) voltage, (I) current, and (R) resistance.
Resistance = Voltage / Current
Ohms = Volts / Amps
Practice with Ohm’s Law 8 48 6 5 45 9 15 30 2 10 150 15 25 100 4 Amps Volts Ohms