Electricity Flashcards
What is the unit for potential difference?
Volts
What is the unit for current?
Amps
What is the unit for resistance?
Ohms
What is the unit for charge?
Coulomb
What is a component?
A small part of something bigger.
What are the three rules for drawing circuit diagrams?
- Draw all wires straight, even if they aren’t in reality
- All bends must be simplified to right angles
- Use the correct circuit symbols
What is charge?
A physical property of matter. Particles can be positively or negatively charged.
Are protons positively or negatively charged?
Positively.
Are electrons positively or negatively charged?
Negatively.
What happens to like charges?
They repel.
What happens to opposite charges?
They attract.
What attracts or repels charges?
An electrostatic force (a push or a pull).
What charge do delocalised electrons carry in a metal?
A negative charge.
What is electricity?
The flow of charge through a conductor; this allows energy to be transferred to devices.
What is a potential difference?
A measure of how much energy is transferred between two points in a circuit.
What is potential difference measured with?
A voltmeter.
What does an electrical charge need to flow through a complete circuit?
A source of potential difference.
What happens when a potential difference pushes an electron?
Work is done on it. Potential differences transfer energy to or from charge.
How do you complete a circuit so that electrical charge can flow through it?
By connecting a metal wire to a closed (complete) circuit with a battery or power supply (a source of potential difference).
What is current?
The amount of charge flowing per second.
What is current measured with?
An ammeter.
What is resistance?
The difficulty for charge to flow through a component.
What does potential difference need to transfer to or from a charge?
Energy.
Which components can provide potential difference?
Battery, cell and power supply.
What does current flowing through a component depend on?
Both the resistance and the potential difference across the component.
What happens if you reduce the resistance of a component?
The current will increase as it is easier for charge to flow through.
What happens if you increase the potential difference of a circuit?
The current will increase.
What is Ohm’s Law?
The equation that states: Potential Difference = Current x Resistance
What does it mean when the resistance of a component remains constant?
It is always a certain difficulty to pass through.
What does it mean when the resistance of a component is variable?
The resistance can change.
Which components can have variable resistances?
- LDRs, thermistors and variable resistors.
- Lamps and diodes can also change resistance depending on potential difference
What does an ohmic conductor obey?
Ohm’s Law. The current is directly proportional to the potential difference.
What does a graph of potential difference vs current for an ohmic conductor look like?
A straight line through the origin; this will only be the case if the temperature is constant.
What is a filament lamp?
A type of light bulb with a high resistance and a thin wire in it.
What happens when current flows through the electrical wire in a filament lamp?
The energy in the electrical pathway is transferred to the thermal store and radiation pathway (light). The bulb gets so hot that it glows white, generating light.
What happens as the potential difference across a filament lamp increases?
More energy is transferred from electrical to thermal.
What happens to the resistance of a filament lamp as it gets hotter?
The resistance increases, which means that less current flows at higher potential differences.
