Chapter 13: Electrical Systems Flashcards
Define electricity.
It is the flow of electrons around a circuit, from negative to positive
What does a battery provide?
It provides the energy to push the electrons in the wire to flow.
What is current?
It is the rate of flow of electrons
What is a circuit?
It is the path that the current flows
What does having a high current in a circuit mean?
Electrons move quickly, thus there will be a brighter bulb.
What does having a low current in a circuit mean?
Electrons move slowly, thus there will be a dimmer bulb.
What is current flow?
Positive to negative
What is the SI unit for current?
Ampere (A)
What is electron flow?
Negative to positive
What is meant by the term ‘cancel out’?
Batteries connected with the same ends will cancel out
What does an ammeter do and how is it connected in a circuit?
Ammeter measures current and it is connected in series.
Describe the current in a parallel circuit.
Total current is the sum of each branching in parallel as the current divides at each junction.
Describe the current in a series circuit.
Total current stays same throughout circuit as rate of electron flow is same as there is only one pathway for current to flow.
Why cant the ammeter be connected in parallel?
The total current divides into two parts because there are different pathways. Larger current goes towards ammeter because it has low resistance. This results in a short circuit and the ammeter will fuse.
Should an ammeter be placed before or after the bulb?
Series: Doesn’t matter because current is same throughout.
What is potential difference across any two points?
It is the amount of energy needed to move one unit charge of electricity from one point to another.
What is the SI unit for potential difference?
Volts (V)
What is a voltmeter for and how is it connected?
It is to measure potential difference and is connected in parallel.
Describe how to calculate the potential difference in a series circuit.
It is the sum of the total potential difference in the circuit.
Describe the potential difference in a parallel circuit.
The total potential difference is the same.
What does resistance do in a circuit?
It opposes the flow of electrons.
What is resistance?
It is the ratio of the potential difference across it to the current flowing through the load.
What is the SI unit of resistance?
Ohm (omega sign)
What factors does the resistance of an object depend on?
Length, type of material, cross-sectional area
What is the relationship between the resistance of an object and its length?
The longer the object, the higher the resistance, the lower the current.
What does a rheostat do?
It allows us to adjust the resistance in a circuit.
What can a rheostat be used for?
In radios to adjust the volume and to adjust the brightness of a light bulb.
What is the relationship between the length and resistance in a rheostat?
Length increases, more resistance
Length decreases, less resistance
What is power?
How much electrical energy is being converted to other forms of energy per second by the electrical appliance.
What is the SI unit for power?
Watts (W)
What are the 3 hazards of electrical appliances we should look out for?
Damaged insulation, overloading and damp conditions
What does the power rating of an appliance tell you?
It tells us how quickly an appliance converts electrical energy to other forms of energy.
When does overloading occur?
When many appliances are plugged into one power outlet at the same time.
What does the rubber insulator of wires do?
It protects us from direct contact with the metal wires.
What happens when the wire’s insulation is damaged?
The wire becomes bare.
Why shouldn’t you touch bare wires under damp conditions?
Electric current may flow through the person, causing them to get electrically shocked.
What are the dangers of overloading?
Large current will flow through the wires and overheat them, which may cause an electrical fire.
What should you do if there is an electrical fire?
Use a Class C fire extinguisher to put out the fire.
What are the 3 wires found in a 3 pin plug?
Live wire, neutral wire and earth wire.
What are the colors of the 3 wires found in the 3 pin plug?
Live wire: Brown
Earth Wire: Green and yellow
Neutral Wire: Blue
What does the live wire do?
It delivers the current to the electrical appliance from the main supply.
What does the earth wire do?
It connects the metal casing of the appliance to the ground. It is a precaution if the appliance is faulty.
What does the neutral wire do?
It delivers back the current to the main supply to complete the circuit.
What are the characteristics of an earth wire?
No current flows through it, it has a low resistance.
What are the 5 safety features found in all household electrical circuits to deal with large currents?
- Switches
- Earth wire
- Circuit breaker
- Fuse
- Double insulation.
What will happen in a damaged kettle?
In the damaged kettle, the wire with high potential is disconnected from the heating coil and touches the metal casing.
The electric potential of the casing increases to ___V.
There is a large potential difference between the ground and the kettle.
Hence, if a person touches the metal casing, the current flows through his body into the ground.
What does a switch do?
It breaks or completes the electrical circuit.
Where is a switch fitted on?
It is fitted onto the live wire.
Why is the switch fitted onto the live wire?
So that when the appliance is switched off, it disconnects the high voltage from an appliance
How does the fuse help in a household electrical system?
It makes use of the heating effect of an electric current to switch off the large current.
What is a fuse?
It is a short and thin wire placed within an insulating capsule and comes in different ratings.
Where is the fuse connected to?
The live wire
What does the fuse prevent?
It prevents excessive high current flowing and overheating of the appliance.
What will happen if a large current passes through the circuit?
It will melt, causing the circuit to be broken. This means that the fuse has been blown.
What will happen if the live wire touches the neutral wire?
Too much current flowing through, short circuit occurs. This causes overheating and will cause an electrical fire.
Will current flow if the live wire is connected to the earth wire?
Yes, since there is a potential difference, current will flow.
What is a circuit breaker?
A safety device that automatically switches off/ trips the electrical supply when there is an excessive flow of current.
Does the circuit breaker need to be replaced?
No
What can cause a circuit breaker to trip?
A short circuit
When will a short circuit in a circuit breaker happen?
When the current flows through a low resistance path rather than its usual path. Too much current flowing through.
What is a double insulation a substitute for?
Earth wire
Which kind of plugs is it usually found in?
2 pin plug
