3.2 One of the main advantages of electricity is that is can be moved with comparative ease from one place to another through electric circuits
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2. One of the main advantages of electricity is that is can be moved with comparative ease from one place to another through electric circuits
1. describe the behaviour of electrostatic charges and the properties of the fields associated with them
Electrostatic charges cause charged particles to move of change direction. Electrostatic charges create a field of charge. This field becomes less intense the further you are away from it.
2. define the unit of electric charge as the coulomb
Electric charge is measured in coulombs. One coulomb is equivalent to the charge of electrons. The charge on one electron is . The charge on one proton is .
3. define the electric field as a field of force with a field strength equal to the force per unit charge at that point:
E = electric field strength (newton/coulomb) (NC − 1) F = force (newton) (N) q = electric charge (coulomb) (C)
Rearranged, F = qE
Example Problem: Question: Calculate the electric force acting on a charge of − 5μC placed in and electric field of 2000NC − 1 acting north.
Solution: F = qE
4. define electric current as the rate at which charge flows (coulombs/ second or amperes) under the influence of an electric field
Current is the rate at which charge flows. 1 ampere = 1 coulomb/second Conventional current runs from + to -. The electron movement is in the opposite direction of conventional current.
5. identify that current can be either direct with the net flow of charge carriers moving in one direction or alternating with the charge carriers moving backwards and forwards periodically
This is known as AC (Alternating Current) and DC (Direct Current).
In DC circuits the current flows at a constant strength in the same direction. However in AC circuits the current changes its direction of flow at a rate of 50Hz.
6. describe electric potential difference (voltage) between two points as the change in potential energy per unit charge moving from one point to the other (joules/coulomb or volts)
7. discuss how potential difference changes at different points around a DC circuit
8. identify the difference between conductors and insulators
Conductors allow electricity to pass through them. Insulators do not allow electricity to pass through them.
9. define resistance as the ratio of voltage to current for a particular conductor:
This formula is know as Ohm’s law and can be rearranged, V = IR.
10. describe qualitatively how each of the following affects the movement of electricity through a conductor:
The longer the material the higher the resistance is.
cross sectional area
The larger the cross sectional area the lower the resistance is. So the thicker the wire then lower the resistance.
The higher the temperature of a material, the higher the resistance is.
Different materials have different resistances. This is called the resistivity of that material.
1. present diagrammatic information to describe the electric field strength and direction:
A positively charged body is one with an absence of electrons. And a negatively charged body is one with an excess of electrons. To make a body negatively or positively charged electrons are removed or added. Note that like charges repel and unlike charges attract. From this information the diagrams below can be derived.
between charged parallel plates
V = Ed Voltage = Electric Field Distance
about and between a positive and negative point charge
2. solve problems and analyse information using:
3. plan, choose equipment for and perform a first-hand investigation to gather data and use the available evidence to show the relationship between voltage across and current in a DC circuit
4. solve problems and analyse information applying:
5. plan, choose equipment for and perform a first-hand investigation to gather data and use the available evidence to show the variations in potential difference between different points around a DC circuit
6. gather and process secondary information to identify materials that are commonly used as conductors to provide household electricity
Copper is commonly used in electrical wiring.