Physics Science

Electricity

Energy

the ability to do work, measured in joules (J)

5 types of potential energy

1. Gravitational Potential Energy (Ep)
2. Chemical Potential Energy (Ecp)
3. Nuclear Energy (En)
4. Elastic Potential Energy (Eep)
5. Electrical Potential Energy (Ee)

4 types of moving energy

1. Kinetic Energy (Ek)
2. Sound Energy (Es)
3. Heat or Thermal Energy (Q)
4. Light Energy (El)

The Law of Conservation of Energy

The law of conservation of energy states that energy can be transferred or transformed but not created or destroyed

The charge to different types of subatomic particles have

neutrons - no charge

protons - positive charge

electrons - negative charge

The law of electrostatic attraction

The law of electrostatic attraction states that objects that are oppositely charged will feel an attraction force towards each other, but objects that are similarly charged will feel a repulsive charge away from each other.

Electron movement

* easiest way to get electron movement is through surface contact
* the objects that the electrons move to would then have an excess of electrons
* the object the electrons moved from would then have a deficit of electrons

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Conducter

Electrons that are not tightly held by their nuclei are called free electrons. Materials that have free electrons allow electrons to flow through them.

e.g. most metals

Insulator

Materials that do not have free electrons and materials that do not allow for electrons to easily flow/ be conducted through through them.

e.g. plastic, rubber, wood, glass, air

Charge Imbalance / Seperation

When two insulators are rubbed together, electrons can be rubbed off of one and onto the other causing an excess on one and a deficit on the other.

Static Electricity

3 Ways a charged object can become neutral

1. the object can come into contact with the ground
2. the object can sit in the air for long periods of time
3. the object can be brought near to an object with the opposite attraction (positive or negative)

Electric Current

The flow of charges from one location to another.

In solids the charge that will flow will always be electrons as the protons are trapped in the nuclei.

How to move electrons in a conductor

One end of the conductor must have an overall negative charge that will repel the electrons and the other end of the conductor must have an overall positive charge to attract the electrons. This method will ensure that they will move form one side to the other.

Current

Measured in Amps (A) (I) on an Ammeter

Electromotive Force (EMF)

Is the energy (per unit charge) provided to a circuit by a power source

Not a force

The larger the deficit on one side and the larger excess on the other the faster the current will be - the faster the voltage will be

Voltage

Measured in Volts (V) (V) on a Voltmeter

Electrical Resistance

The opposition to electron flow provided by a material

Resistance

Measured in Ohms (Ω) (R) on an Ohmmeter

Ohm’s Law

V=IR

Voltage = Current x Resistance

Gradient = Resistance

Gradient = (change in y) / (change in x)

or

Gradient = rise / run

or

Gradient = change in voltage / change in current

Ohmic vs Non-Ohmic Resistors

Resistors that obey Ohm’s Law are called Ohmic Resistors and will have a constant resistance - the gradient will be a straight line

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Resistors that do not obey Ohm’s Law are called Non-Ohmic Resistors and will not have a constant resistance - the gradient will be curved

Load

Any part of an electrical circuit that transforms electrical potential energy into another kind of energy

Measuring Voltage

Voltage (EMF or Potential Difference)

Must be wired in parallel to the circuit (not actually inside)

Measures across power sources (EMF) or a load (PD)

Measuring Current

Must be wired in series (inside the circuit)

electrons need to flow through it

Measuring Resistance

Must be wired in parallel (not actually inside)

Should be around a load that doesn’t have a current at that moment

Power

The amount of energy transformed by a load every second

Watt (W)

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1 watt = 1 joule / 1 second

2 ways to calculate power

P = E / t (E = energy)

or

P = IV

Atom

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the basic unit of matter and the smallest particle that retains its characteristics in a chemical reaction

Free Electrons

an electron that is not tightly held by its nucleus

Ion

An atom with either a positive or negative charge

Potential Difference

the energy (per unit charge) transformed by a load, measured in volts (V)

Resistor

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an object that resists the flow of electrons