Unit 20- electricity and magnetism

What are the main topics covered in Unit 20?

Electrical circuits, properties of magnets, magnetic fields, electromagnets, and measuring current and voltage (potential difference).

What is an ammeter used for?

A device used to measure electric current.

What is the unit of current?

Ampere (A).

What is the function of a battery?

Converts chemical energy to electrical energy.

What is a cell in the context of electricity?

A store of internal energy that can be transferred as an electric current in a circuit.

Define a circuit.

A closed loop through which current moves - from a power source, through a series of components, and back into the power source.

What is a circuit diagram?

A diagram that represents an electric circuit using lines and symbols.

What is a conductor?

A material which allows charge to move easily through it.

What is electric charge?

The electrical state of an object, which can be positively charged or negatively charged.

What is electric current?

The movement of electrically charged particles, for example, electrons moving through a wire or ions moving through a solution.

What subatomic particle moves in wires causing an electric current?

Electron.

Describe components connected "in parallel".

In a parallel circuit, the current divides into two or more paths before recombining to complete the circuit.

Describe components connected "in series".

Connected to a circuit in such a way that the same current flows through each component in turn.

What is an insulator?

Material that does not allow charge or heat to pass through it easily.

What is the unit of electrical resistance?

Ohms (Ω).

What is potential difference (voltage)?

A measure of the energy given to the charge carriers in a circuit, and it is the voltage between two points that makes an electric current flow between them.

What is resistance?

The opposition in an electrical component to the movement of electrical charge through it.

What is the unit of voltage?

Volt (V).

What is a voltmeter used for?

A device used to measure potential difference or voltage.

What two things are needed for an electric current to flow?

Something to transfer energy to the electrons (like a battery) and a complete path for the electrons to flow through (a complete electric circuit).

What is the purpose of a switch in a circuit?

To break the circuit and stop the electric current when desired.

How is the symbol for a battery made from cell symbols?

By joining two or more symbols for a cell together.

What does the letter 'I' indicate in electrical circuits?

Current.

What is the direction of current typically shown as?

From + towards - in the circuit.

How is current measured?

By connecting an Ammeter in series with the component through which the current is to be measured.

How is potential difference measured?

Using a Voltmeter connected in parallel across the component.

How does adding more cells affect the potential difference?

If the cells point in the same direction, the more cells, the bigger the potential difference.

What is the relationship between current and potential difference for measuring devices?

An ammeter measures current and is connected in series; a voltmeter measures potential difference and is connected in parallel[cite: 68].

In a series circuit with two lamps, how does the current in lamp A compare to lamp B?

Both get exactly the same current because they are in series.

What happens in a series circuit if a lamp breaks or a component is disconnected?

The circuit is broken, and all components stop working.

What is an advantage of series circuits?

They are useful if you want a warning that one of the components in the circuit has failed, and they use less wiring than parallel circuits.

Is current used up in a series circuit?

No, the current is the same everywhere in a series circuit, even with many components.

In a parallel circuit, what happens if a lamp breaks or a component is disconnected from one branch?

The components on different branches keep working.

Why are homes typically wired with parallel circuits?

Because if one component fails, everything else continues to work.

How is current handled in a parallel circuit?

The total current is shared between the components; it divides when it reaches the branches and adds again where the branches meet.

If lamps in a parallel circuit are not identical, how does resistance affect the current through each?

The greater the resistance of a lamp, the smaller the current that flows through it.

What is resistance in a circuit?

The opposition in an electrical component to the movement of electrical charge through it.

What is the effect of higher electrical resistance on the current in a circuit?

The more electrical resistance a circuit has, the lower the current in the circuit.

How does adding more components in series affect resistance?

The resistance increases.

How is the resistance of a component calculated?

Resistance = potential difference ÷ current (R=V/I).

What is an electrical conductor?

A material that has a low resistance.

What is an electrical insulator?

A material that has a high resistance.

Give examples of electrical conductors.

Metal elements (All Metals), Graphite, Mixtures of metals (e.g., brass, solder).

Give examples of electrical insulators.

Most non-metal elements (e.g., sulfur, oxygen), Diamond, Plastic, Glass, Wood.

What is electrical power?

The rate at which energy is transferred (or changed).

What is the equation for power in terms of energy and time?

Power = Energy / time (P=E/t).

What is the unit of power?

Watts (W).

How is electrical power calculated using voltage and current?

Power = Voltage x Current (P=IV).

What is a key safety feature related to current in appliances?

A fuse, which blows if the current gets too high, stopping the circuit from working and preventing overheating.

What is a key advantage of electromagnets over permanent magnets?

They can be turned on and off, their strength can be varied, and the direction of the magnetic field can be reversed.