Electricity Flashcards
What is the unit of measurement for current?
Amperes (A)
Current is the rate of flow of charge in a circuit.
How is current (I) calculated?
I = Q/t
Where Q is charge in coulombs and t is time in seconds.
What is conventional current?
The rate of flow of positive charge
It flows in the opposite direction to the flow of electrons.
How is current conserved in a circuit?
Charge is always conserved
Current is conserved at a junction.
What instrument is used to measure current?
Ammeter
It is connected in series with the component.
What is potential difference (V) measured in?
Volts (V)
1 V = 1 J/C (joules per coulomb).
How is potential difference calculated?
V = E/Q
Where E is work done and Q is charge.
How is potential difference measured?
Voltmeter
It is placed in parallel across the component.
What is the relationship between potential difference and current?
V = IR
Higher potential difference results in greater current.
What is the unit of resistance?
Ohms (Ω)
Resistance is the difficulty for current to flow through a component.
How is resistance (R) calculated?
R = V/I
Where V is potential difference and I is current.
What characterizes an ohmic conductor?
Current is directly proportional to voltage
It has constant resistance.
What happens to resistance in a non-ohmic conductor like a filament lamp?
Resistance changes as voltage and current change
This is due to temperature effects on the material.
What is a thermistor?
A resistor whose resistance decreases as temperature increases
Used in temperature sensing applications.
What is a light dependent resistor (LDR)?
A resistor whose resistance decreases as light intensity increases
Commonly used in light-sensing circuits.
What are the characteristics of a series circuit?
Components are connected end to end in one loop
The same current flows through every component.
What is the relationship between potential difference and resistance in a series circuit?
The potential difference is shared across each component depending on their resistance.
The sum of the potential differences across the components is equal to the total potential difference across the supply. Components with a higher resistance have a greater potential difference across them.
How is total resistance calculated in a series circuit?
Total resistance is the sum of the resistances of each component: R = R1 + R2 + …
This indicates that the total resistance increases as more components are added in series.
Describe the configuration of components in a parallel circuit.
Components are connected to the power supply in separate branches.
Each branch allows current to flow independently.
What happens to the current in a parallel circuit?
The current is shared between each branch.
The sum of the currents in the separate branches is equal to the current through the source.
What is the potential difference across branches in a parallel circuit?
The potential difference is the same across every branch.
This uniformity makes parallel circuits advantageous for connecting multiple devices.
What is an advantage of connecting lamps in parallel?
If one lamp breaks, current can still pass through the rest.
This ensures that not all lamps go out if one fails.
List three hazards associated with electricity.
- Damaged insulation
- Overheating of cables
- Damp conditions
Each hazard poses a risk of electric shock or fire.
What role does a fuse play in an electrical circuit?
A fuse protects the circuit by melting if the current is too high.
Fuses have a current rating slightly higher than the device’s operating current, commonly 3A, 5A, and 13A.
