Electricity

Question 1

What is Electricity?

Answer 1

• Electricity is a form of energy that results from either the build up of charge (static electricity) or the flow of charge (current electricity)

Question 2

Types of Charge

Answer 2

• Positive (+)
• Negative (-)

Question 3

Atoms

Answer 3

• All objects are made out of atoms. Each atom contains three different types of subatomic particles
• Protons (positive charge)
• Neutrons (neutral charge)
• Electrons (negative charge)
• Atoms contain the same number of protons and electrons and the positive and negative charges are cancelled out meaning the atom has no overall charge

Question 4

Static Electricity

Answer 4

• Static Electricity is created when there is an imbalance of charge on objects
• The object either loses or gains negative charges (electrons)
• Objects that lose negative charges (electrons) become positively charged overall
• Objects that gain negative charges (electrons) become negatively charged overall
• The charge build up is called electrostatic charge because it stays on the object

Question 5

Current Electricity

Answer 5

• Current Electricity involves the movement of charges (electrons)
• These charges may continue steadily moving for a period
• When charge passes through electrical components, it transfers energy to that component
• Depending on what that component is, it converts that energy into other forms of energy like movement, light and heat.

Question 6

Conductors

Answer 6

• A conductor is an object or type of material that allows the flow of an electrical current to occur through it, e.g. a metal wire is a common electrical conductor
• An electrical current is a flow of negatively charged electrons
• Metals contain mobile valence electrons which are free to move around

Question 7

Examples of Conductors

Answer 7

• Metals
• Animals
• Salts in water

Question 8

Insulators

Answer 8

• An insulator is an object or type of material that does not allow for the flow of an electrical current to occur through it
• Non-metal atoms tightly hold on to their electrons and don’t release them easily

Question 9

Examples of Insulators

Answer 9

• Plastic
• Wood
• Paper
• Wool

Question 10

Circuits

Answer 10

• An electric circuit is a pathway that electrons can pass through
• Negatively charged electrons leave the negative terminal of the battery and travel towards its positive terminal
• A circuit needs an energy source, an energy user (e.g. a globe) and wires to connect them all
• The circuit usually has a switch as well

Question 11

Ammeter

Answer 11

• An ammeter measures the current (no. of electrons passing a given point in a circuit every second)

Question 12

Voltmeter

Answer 12

• A voltmeter measures voltage (how much energy is supplied to push the electrons in the current)

Question 13

Current

Answer 13

• Current is a measure of the no. of electrons passing a given point in a circuit every second
  i.e. related to the speed of electrons
• Measured in Amperes
• Measured using an Ammeter

Question 14

Voltage

Answer 14

• Voltage is a measure of how much energy is supplied to push the electrons in the current
• Measured in Volts
• Measured using a Voltmeter

Question 14

Voltage of a Circuit

Answer 14

• Voltage is the difference in electric potential energy between two points per electric charge
  i.e. it’s a measure of the energy drop across a circuit or any two points in a circuit
• The unit of voltage is volts
• It is not a measure of the speed of electrons through a circuit
• Current, the measure of electron speed, is measured using an ammeter

Question 15

Series Circuit

Answer 15

• In a series circuit, the current runs through every appliance
• Globes get duller and duller as you add more of them to a series circuit because each time you add a globe you increase the resistance of the circuit, and the current slows down

Question 16

Parallel Circuit

Answer 16

• A parallel circuit has a number of branches, with each branch having its own components
• Each time another appliance is added in parallel, more current is drawn from the power source
• There is no change in brightness of globes when more appliances are added in a parallel circuit
• An increased no. of electrons is drawn from the power source to cover the extra appliance
• Each electron will only pass through one appliance, only to rejoin with the other electrons when they return to the power source

Question 17

Parallel Circuits con.

Answer 17

• Remember: each time another appliance is added in parallel, more current is drawn from the power source
• If too many appliances are added then too much current could be drawn from the power supply
• Safety switches, which break the circuit, are used to prevent these power surges
• There is no change in brightness of globes as more appliances are added
• The circuits around your home are connected in parallel
• This allows every appliance (e.g. a hairdryer) to be controlled independently and supplied with 240 V

Question 18

Resistance

Answer 18

• The resistance of an electrical component refers to how difficult it is for electrons to flow through it
• The unit of resistance is the ohm (Ω)
• Good electrical conductors have low resistance (e.g. metal wires have zero resistance)
• Insulators have high resistance
• A small light globe may have a resistance of 40 Ω
• A refrigerator may have a resistance of 50,000 Ω

Question 19

Current and Voltage in Series Circuits

Answer 19

• In a series circuit the same current passes through each resistor (e.g. all globes)
• Hence, voltage is split between each resistor

Question 20

Completing a Circuit- Fuses

Answer 20

• Electrons will always take the path of least resistance when passing through a circuit
• A fuse wire is inserted into circuits to prevent sudden bursts of charges when electrons take an undesirable short circuit back to the power source

Question 21

Current and Voltage in Parallel Circuits

Answer 21

• In a parallel circuit extra current is drawn from the supply with each new appliance
• The voltage is the same across each resistor as the current is split between them