the particulate nature of matter

False. This circuit symbol represents a cell.

The symbol for a switch is:

False. This circuit symbol represents a variable resistor.

The circuit symbol for a battery is two or more cells joined together.

The symbol for a voltmeter is:

This circuit symbol represents a potentiometer.

The symbol for a thermistor is:

True. This circuit symbol represents a heating element.

The symbol for an ammeter is:

This circuit symbol represents a light emitting diode (LED).

A thermistor is a resistor whose resistance changes depending on its temperature.

This circuit symbol represents a light dependent resistor (LDR).

A potentiometer is a resistor with a sliding contact that forms an adjustable voltage divider.

Electric current is the rate of flow of charge carriers.

The charged particles that flow in electrical circuits are electrons.

Conventional current is the flow of positive charge from the positive terminal of a cell to the negative terminal.

Direct current (d.c.) flows around a circuit in one direction.

The equation for current as the flow of charge is: Where:

True. Electrons do flow around a circuit towards the positive terminal, while conventional current flows towards the negative terminal. It is electrons that actually form the current, but the idea of conventional current was in use before the electron was discovered.

The current in the circuit is 10 A.

The amount of charge that has passed through the ammeter in this time is 3 C.

Electric potential difference is the work done per unit charge on moving a positive charge between two points along the path of the current.

The equation linking potential difference, work done and charge is Where:

True. One volt is equal to one joule per coulomb, 1 V = 1 J C–1.

False. A cell or battery provides the source of potential difference in a d.c. circuit.

False. The electrons in the circuit are the delocalised electrons in the metal of the wires and components. They flow around the closed circuit when a potential difference is applied.

The electronvolt is the amount of energy needed to move an electron through a potential difference of one volt.

One electronvolt is equal to .

12 eV in J is

An electrical conductor is a material that allows charge (usually electrons) to flow through it easily.

Examples of electrical conductors are:

Metals are good electrical conductors because metals have delocalised electrons that flow when a potential difference is applied.

An electrical insulator is a material that has no delocalised electrons, so it does not allow charge to flow easily.

Examples of electrical insulators are:

Static electricity occurs when charge builds up on the surface of an insulator and is discharged when brought into contact with a conductor.

An ideal ammeter has zero resistance, such that all the current passes through it.

An ideal voltmeter has infinite resistance, such that no current passes through it.

The resistance of a component is the ratio of the potential difference across the component to the current flowing through it.

The equation for resistance known as Ohm's law is Where:

False. The greater the resistance of a component, the lower the current flowing through it.

The SI base units for 1 Ω are kg m–2 s–3 A–2.

True. For resistance calculations, mA and kV must be converted into A and V.

True. Resistance is caused by collisions between flowing electrons and the metal ions in the conductor.

The factors affecting resistance are:

True. The resistance of a wire is directly proportional to its length.

False. The resistance of a wire is inversely proportional to its cross-sectional area.

Resistivity is the electrical resistance of a conductor of unit cross-sectional area and unit length.

The equation for resistivity is Where:

Metals have low values of resistivity, and insulators have high values.

The equation for the cross-sectional area of a circle is Where:

The equation for the cross-sectional area of a circle in terms of diameter is Where:

The gradient of an I-V graph represents the resistance of a component.

A linear I-V (current-voltage) graph shows

This is the I-V graph for a fixed resistor or a wire (at a constant temperature).

This is the I-V graph for a filament lamp.

This is the I-V graph for a diode.

False. As the current through a filament lamp increases, the resistance increases.

The resistance of a filament lamp increases as the voltage is increased because

The I-V graph for a diode shows they have

False. Current is the same everywhere in a series circuit.

True. In a parallel circuit, the current from the power source is larger than the current in each branch.

True. The amount of current flowing in any circuit depends on the potential difference and resistance in the circuit.

True. Current is conserved at a junction in a parallel circuit because charge is always conserved.

False. Current will only split equally at a junction if the resistance in each branch is equal.

The current in a series circuit is the same through all the components. This can be expressed mathematically as:

The total current through the components in a parallel circuit is equal to the sum of the individual currents through each branch. This can be expressed mathematically as:

False. When several cells are connected in series, the potential difference across them all is the sum of the separate potential differences.

The total potential difference across the components in a series circuit is equal to the sum of the individual potential differences across each component. This can be expressed mathematically as:

The total potential difference across an arrangement of parallel resistances is the same as the potential difference across one branch in the arrangement of the parallel resistances. This can be expressed mathematically as:

True. The combined resistance of two resistors in parallel is less than that of either resistor by itself.

When two or more resistors are connected in series, the combined resistance is the sum of the individual resistances. This can be expressed mathematically as:

When two or more resistors are connected in parallel, the combined resistance is the sum of the reciprocals of the individual resistances. This can be expressed mathematically as:

Adding components to a circuit increases the total resistance of the circuit, so the current would decrease (for a constant potential difference).

If the potential difference of the power source is increased, but everything else in the circuit remains constant, the current will increase.

Electrical power is the rate at which energy is transferred or dissipated by a resistor.

True. Work is done when energy is transferred by moving charges in a circuit.

The equation for electrical power is:
Where:

The equation for electrical power is:
Where:

The equation for electrical power is: Where:

The equation for energy transferred is:
Where:

Chemical cells use the energy stored in chemicals to arrange charges in a way that produces a potential difference.

Solar cells use the radiant energy from the Sun to produce a potential difference.

Electrical generators use the energy from burning fuels to convert kinetic energy into electric potential energy to produce a potential difference.

Wind generators use the energy from moving air to convert the kinetic energy of wind into electric potential energy to produce a potential difference.

Advantages of single-use alkaline batteries are:

Disadvantages of single-use alkaline batteries are:

Advantages of lithium-ion batteries are:

Disadvantages of lithium-ion batteries are:

Advantages of lead-acid batteries are:

Disadvantages of lead-acid batteries are:

Advantages of photovoltaic cells are:

Disadvantages of photovoltaic cells are:

Advantages of wind generators are:

Disadvantages of wind generators are:

Advantages of fossil fuel generators are:

Disadvantages of fossil fuel generators are:

Electromotive force (emf) is the total energy transferred in a source of electrical energy per unit charge passing through it.

Internal resistance is the resistance of a source of electrical energy, such as batteries, as they are not perfect conductors.

Terminal potential difference is the potential difference across the terminals of a source of electrical energy when it is supplying a current to a circuit.

'Lost volts' refer to the voltage drop, or decrease in potential difference, that occurs when a source of electrical energy supplies a current to a circuit.

The equation linking emf and internal resistance is:
Where:

False. When the internal resistance is zero, the terminal p.d. of a cell is equal to its emf. This is when no current flows.

True. When a current flows, the terminal p.d. of a cell will be less than its emf. This is because there will be a potential drop across the internal resistance.

A thermistor is a temperature-dependent resistor. This means its resistance changes depending on its temperature.

When the temperature of a thermistor is increased, its resistance decreases.

LDR stands for light-dependent resistor. This means its resistance changes depending on the intensity of light on it.

When light intensity on an LDR is increased, its resistance decreases. (Remember: Light Decreases Resistance - LDR)

For a thermistor, the relationship between resistance and temperature is

For an LDR, the relationship between resistance and light intensity is

A variable resistor is a resistor that can change the resistance by changing the length of the wire that makes up the circuit. This is because a longer length of wire has more resistance than a shorter length of wire.

A potentiometer is a type of variable resistor that uses a sliding contact to vary the potential difference in a circuit.