Circuits + Household Electricity Flashcards
What is a current?
A current is a ‘body’ moving in a definite direction
How do you calculate Current?
Current = Charge / time
Or
I = Q / t
How do you calculate the Number of Electrons?
Number of Electrons = Charge / Charge of 1 electron
What is the Potential Difference (Voltage) between two points in an electrical circuit?
It is the Work Done per Coulomb Charge that passes between the points.
How do you calculate the Potential Difference?
Potential Difference = Work Done / Charge
Or
V = W / Q
What is Resistance in a circuit?
Resistance in a circuit is the opposition to the flow of charge.
What are the factors that effect the amount of resistance in a circuit?
- Length og wire
- Diameter / Cross-sectional area of a wire
- Heat
- Conductivity
How do you calculate Resistance?
Resistance = Potential Difference / Current
Or
R = V / I
(V = I x R
What is Ohm’s law?
The current through a conductor is directly proportional to the Voltage across two points.
E.g. If the Current doubles then the Voltage will also double
What is the rule for a Light Dependent Resistor?
Brightness Increases, Resistance Decreases
Or
BIRD
What is the rule for a thermistor?
Temperature Up, Resistance Down
Or
TURD
What is a Series Circuit?
A Series Circuit is only 1 loop meaning the current only has one path to flow through.
What is the rule for Current in a circuit?
It is the same at all points of the circuit
What is the rule for Potential Difference in a circuit?
It is shared between components
V supply = V¹ + V² + V³…
How do you calculate the resistance in a Series Circuit?
Resistance Total = R¹ + R² + R³…
What is a Parallel Circuit?
In a Parallel circuit there are several loops, this means the current has more than one path to flow through.
What is the resistance in a Parallel Circuit?
The total resistance of two (or more) components in a parallel is less than the resistance of the resistor with the least resistance.
What is the Current in a Parallel Circuit?
The total current through the whole circuit is the sum of the currents through each branch.
What is the advantages of Parallel Circuits?
- You can control each branch with a switch
2. If one branch fails due to a component, the rest of the circuit will remain to work
What is an Electrical Field?
Electrical Fields exist around charged objects and when things enter this field they will experience a force.
What is an Alternate Current?
A Current that changes direction, comes from the National Grid
What is a Direct Current?
A Direct Current is a Current that only flows in one direction.
What is the Frequency and Voltage of the National Grid?
Frequency = 50 Hz
Voltage = 230 V
What is the Colour, Voltage and Function of a Live Wire?
Brown
230 V
Provides the large alternating Potential Difference between it and the neutral wire so a alternating current is produced to power the appliance.
What is the Colour, Voltage and Function of a Neutral Wire?
Blue
Close to 0 V
Provides a Potential Difference close to 0 V for the live wire to produce a large alternating potential difference berween the two wires.
What is the Colour, Voltage and Function of the Earth Wire?
Yellow and Green
0 V
Connected to metal cases of appliances to stop it becoming live if the live wire touches the case. This stops the risk of electric shock to the user.
What does a Fuse do?
A fuse melts and creates a circuit breaker stopping the flow of the current to the appliance. This can therefore stops house fire.
How do you calculate Power?
Power = Current x Potential Difference
P = I x V
What is the National Grid?
The National Grid is a system of cables and transformers.
What is a Step-down transformer?
Decreases the Voltage and increases the Current
Found near homes, offices and schools
What is a Step-up transformer?
Increases the Voltage and decreases the Current
Found near Power Stations
What are the 3 ways to calculate Energy?
E = Q x V
E = P x t
E = I x t x V
