Electricity Flashcards
What is current?
A measure of the flow of electrons around a circuit
What is the unit of Electric Current?
Amperes, amps, or ‘A’
What is Potential Difference?
The force driving the flow of electrons around a circuit
What is Resistance?
Everything that resists or opposes the flow of electrons in a circuit
What Are The Units Of Potential Difference?
Voltage, volts, and ‘V’
What is the unit of Resistance?
Ohms (Ω)
What is the symbol for a filament lamp?
A circle with a cross inside
What is the direction of current flow?
- Electrons flow - Negative → Positive
- Conventional current - Positive → Negative
What are the circuit symbols for a cell
A cell is one long line (positive) and one short line (negative)
What are the circuit symbols for a battery?
Two or more cells joined together
What is the definition of charge (Q)?
The measure of the total current that flows within a certain period of time
What is the unit for charge?
Coulombs (C)
What is the equation for charge (Q)?
Q=I×t
Where:
Q = Charge (C)
I = Current (A)
t = Time (s)
What is a series circuit?
A circuit with only a single loop, where components are connected one after another
What happens if a component in a series circuit is disconnected?
The whole circuit stops working
How is voltage shared in a series circuit?
The total voltage of the battery is shared across all components
How is voltage across a single component calculated?
V=I×R
What is the function of a voltmeter?
- Measures the potential difference across a component
What happens to components with higher resistance in a series circuit?
Components with higher resistance get a larger share of the total voltage
What is a parallel circuit?
A circuit with more than one loop, where each loop typically contains only one component
What happens if one component in a parallel circuit breaks?
The overall circuit remains intact, and other components continue working
How is voltage shared in a parallel circuit?
shared equally across all branches of the circuit
How is current shared in a parallel circuit?
- The total current splits between the loops
- The sum of the currents in all loops equals the total current of the circuit
How does resistance affect current in a parallel circuit?
Adding more resistors decreases the total resistance, increasing the total current.
What happens to the total resistance when more components are added in parallel?
The total resistance of the circuit decreases
What is the relationship between total resistance and loops in parallel?
The more loops added, the lower the total resistance of the circuit
Why are parallel circuits more practical than series circuits?
In parallel circuits, if one component breaks, the rest of the circuit still works
What are the 3 formulas for energy?
Energy (E) = Power (P) x Time (t)
Energy (E) = Voltage (V) x Current (I) x Time (t)
Energy (E) = Charge (Q) x Voltage (V)
What are the key characteristics of the mains supply in the UK?
The mains supply is an alternating current (AC) of 230 volts and 50 hertz
What are the three wires in a three-core cable?
- Live wire (Brown)
- Neutral wire (Blue)
- Earth wire (Green & Yellow)
What is the function of the live wire, and what is its potential difference?
- Provides the alternating potential difference from the mains supply
- P.D: 230V
What is the function of the neutral wire, and what is its potential difference?
- Completes the circuit by carrying away current
- P.D: 0 Volts
What is the function of the earth wire, and what is its potential difference?
- Stops the appliance casing from becoming live
- P.D: 0 Volts
What happens if the live wire touches the casing of an appliance?
Provides a safe pathway for current, preventing electric shocks
Why is touching the live wire dangerous?
Has a potential difference of 230 volts, and since humans have a potential difference of 0 volts, a large current will flow through the body, causing a shock
How does electricity flow in a circuit with a three-core cable?
- Flows into the device through the live wire
- Flows out through the neutral wire
Why should you never touch a plug socket, even if it’s switched off?
The live wire still has a potential difference, so contact could result in an electric shock
What are the wires inside a three-core cable made of, and why?
The wires are made of copper because it conducts electricity well
Why are wires coated with plastic?
The plastic acts as an insulator for safety
What are surges in an electrical circuit?
Sudden increases in current
Why do surges happen?
- Circuit changes
- Due to faults in the circuit or appliance
What can electrical surges cause?
- Damage appliances
- Cause fires
- Result in electric shocks
What is the function of a fuse in a circuit?
Breaks the circuit by melting when the current becomes too high, preventing further current flow
How do you select a fuse rating for an appliance?
Choose a fuse a few amps higher than the appliance’s normal operating current
What are the advantages of fuses?
- Simple
- Cheap
What are the Disadvantages of fuses?
Permanently damaged after a surge and need replacing
How do circuit breakers differ from fuses?
Circuit breakers trip when the current is too high
but can be reset instead of replaced
What is the role of the earth wire?
Provides an alternative pathway for current to flow away, preventing electric shocks
What is double insulation?
Double insulation covers appliances with plastic casing
Why is double insulation is useful?
So there are no exposed metal parts, preventing electric shocks
What wires are found in appliances with double insulation?
- Live wires
- Neutral wires
What happens if a live wire touches an appliance’s casing?
Make the casing live, and touching it could result in a severe electric shock
What are the benefits of circuit breakers over fuses?
- Circuit breakers - can be reset after a surge
- Fuses - must be replaced
How are fuses and circuit breakers similar?
Both break the circuit when the current gets too high, preventing damage and electric shocks
