Electrical charge and current

Figure 1 shows two lamps in series in a circuit.

The resistance of each lamp is 12 Ω.

Calculate the total resistance of the lamps in the circuit.

total resistance of lamps =_........

The current in a lamp in Figure 1 is 0.50 A.

The resistance of the lamp is 12 Ω.

Calculate the voltage across this lamp.

Use the equation

V = I × R

The voltage across a different lamp is 4.5 V.

The current in this lamp is 0.40 A.

Calculate the energy transferred to the lamp in 5 minutes.

Use the equation

E = I × V × t

energy transferred =_........

Figure 2 shows a circuit with a switch, two ammeters and two resistors in series with a cell.

Which of these statements is true for the circuit in Figure 2?

The resistance of the circuit is increased by adding one resistor to the circuit.

State how increasing the resistance changes the current in the circuit.

Figure 19 shows two metal plates.

The plates are charged by a very high voltage (potential difference).

Draw, on Figure 19, the shape and direction of the electric field between the two plates.

Figure 20 shows a device that removes small particles of soot from sooty air.

There is a large potential difference between the metal tube and the metal rod in the centre of the tube.

This large potential difference causes the soot particles to gain a negative charge as they pass between the rod and the tube.

The soot particles have

Explain why, in Figure 20, the charged soot particles move towards the metal tube.

When the soot particles reach the metal tube, the charge on them changes.

State how the charge on them changes.

The metal tube does not become charged when the soot particles reach it.

Explain why the metal tube does not become charged.

There is a current of 2.5 mA in a circuit.

Calculate the amount of charge that moves past a point in the circuit in 80 seconds.

State the unit of charge.

If you’re taking GCSE (9–1) Combined Science or GCSE (9–1) Physics, you will need these equations:

HT = higher tier

distance travelled = average speed × time
acceleration = change in velocity ÷ time taken	a v t u
force = mass × acceleration	F = m × a
weight = mass × gravitational field strength	W = m × g
HT momentum = mass × velocity	p = m × v
change in gravitational potential energy = mass × gravitational field strength × change in vertical height	∆GPE = m × g × ∆h
kinetic energy = 1/2 × mass × (speed)2	KE 21 m v2
efficiency = useful energy transferred by the devicetotal energy supplied to the device
wave speed = frequency × wavelength	v = f × λ
wave speed = distance ÷ time	v xt
work done = force × distance moved in the direction of the force	E = F × d
power = work done ÷ time taken	P Et
energy transferred = charge moved × potential difference	E = Q × V
charge = current × time	Q = I × t
potential difference = current × resistance	V = I × R
power = energy transferred ÷ time taken	P Et
electrical power = current × potential difference	P = I × V
electrical power = (current)2 × resistance	P = I2 × R
density = mass ÷ volume	mV

force exerted on a spring = spring constant × extension F = k × x

If you’re taking GCSE (9–1) Physics, you also need these extra equations:

moment of a force = force × distance normal to the direction of the force
pressure = force normal to surface ÷ area of surface	P FA
HT potential difference across secondary coilpotential difference across primary coil nnumber of turns in primary coilumber of turns in secondary coil	VVpS NNpS
to calculate pressure or volume for gases of fixed mass at constant temperature	P1 × V1 = P2 × V2
HT pressure due to a column of liquid liquid × gravitational field strength= height of column × density of	P = h × ρ × g

Figure 5 shows two metal plates.

The plates are charged by a very high voltage (potential difference).

Draw, on Figure 5, the shape and direction of the electric field between the two plates.

Figure 6 shows a device that removes small particles of soot from sooty air.

There is a large potential difference between the metal tube and the metal rod in the centre of the tube.

This large potential difference causes the soot particles to gain a negative charge as they pass between the rod and the tube.

The soot particles have

Explain why, in Figure 6, the charged soot particles move towards the metal tube.

When the soot particles reach the metal tube, the charge on them changes.

State how the charge on them changes.

The metal tube does not become charged when the soot particles reach it.

Explain why the metal tube does not become charged.

There is a current of 2.5 mA in a circuit.

Calculate the amount of charge that moves past a point in the circuit in 80 seconds.

State the unit of charge.

A student connects a resistor across the terminals of a 9 V battery.

There is a current of 6 mA in the resistor.

Calculate the resistance of the resistor.

Describe how an additional component could be used to vary the current in the resistor.

A voltmeter has four different scales.

Which one of these scales would be most suitable to measure a voltage of 0.85 V?

*(c) The table in Figure 23 gives some information about series and parallel circuits.

Describe how a student can use ammeters and voltmeters to investigate the information given in Figure 23.

Your answer should include

• circuit diagrams showing how the currents and voltages can be measured

• a comparison of the results that would be expected

Space for circuit diagrams

Answer lines for this question are on page 37.

Figure 1 shows a circuit containing a battery and four other components.

Label the four components in Figure 1, using words from the box.

The circuit in Figure 1 is switched on.

A charge of 1.2 C leaves the battery in a time of 4.0 s.

Calculate the current in the circuit.

Use the equation

current =_........

Figure 3 shows the parts in an electrical circuit.

Draw the circuit diagram of this electrical circuit in the space provided.

The battery symbol and some of the connecting wires have been drawn for you.

Figure 4 shows the current flowing into and out of point P in part of a circuit.

Which of these is the value of current I ?

There is a current of 0.46 A in a lamp.

Calculate the total charge that flows through the lamp in 30 seconds.

Use the equation

charge = currenttime in seconds

The voltage across the lamp is 6.0 V.

The current in the lamp is 0.46 A.

Calculate the energy transferred to the lamp in one minute.

Use the equation

energy transferred = currentvoltagetime in seconds

energy transferred =_........

The voltage (potential difference) across a length of wire is 1.5 V.

A charge of 0.042 C flows through the wire.

Calculate the energy transferred.

Use the equation

Figure 20 shows some of the apparatus that students use to determine the resistance of a piece of iron wire.

Add connecting wires, a voltmeter and an ammeter to complete the circuit in Figure 20 so that the students can determine the resistance of the piece of iron wire.

The students extend the investigation to determine how the resistance of the iron wire changes with its length.

Give the name of one additional piece of apparatus the students would need.

Figure 21 shows a graph of the results.

Draw a straight line of best fit on Figure 21.

Use Figure 21 to estimate the resistance of a 100 cm length of the iron wire.

The variable resistor shown in Figure 20 is used to prevent the iron wire from becoming too hot.

Explain how the variable resistor is used to prevent the iron wire from becoming too hot.

The potential difference (voltage) across another piece of wire is 1.56 V.

The current in the wire is 0.45 A.

Calculate the resistance of this piece of wire.

Use the equation

Figure 3 shows some of the apparatus that students use to determine the resistance of a piece of iron wire.

Add connecting wires, a voltmeter and an ammeter to complete the circuit in Figure 3 so that the students can determine the resistance of the piece of iron wire.

The students extend the investigation to determine how the resistance of the iron wire changes with its length.

Give the name of one additional piece of apparatus the students would need.

Figure 4 shows a graph of the results.

Draw a straight line of best fit on Figure 4.

Use Figure 4 to estimate the resistance of a 100 cm length of the iron wire.

The variable resistor shown in Figure 3 is used to prevent the iron wire from becoming too hot.

Explain how the variable resistor is used to prevent the iron wire from becoming too hot.

The potential difference (voltage) across another piece of wire is 1.56 V.

The current in the wire is 0.45 A.

Calculate the resistance of this piece of wire.

Use the equation

This question is about electrical circuits.

Draw one straight line from each circuit symbol to its description.

Figure 1 shows a lamp in a circuit.

The lamp is switched on.

The current in the lamp is a flow of

The current in the lamp is 0.21 A.

Calculate the charge that flows through the lamp in a time of 300 s.

State the unit of charge.

Use the equation

charge = current × time

Figure 1 shows an electrical circuit.

Draw a circuit diagram of the electrical circuit in Figure 1 in the space below.

When the current in a lamp is 0.15 A, the resistance of the lamp is 40 Ω.

Calculate the voltage across the lamp.

Use the equation

V = I × R

Figure 2 shows an ammeter that can read up to 5 A.

State the value of the current shown on the ammeter in Figure 2.

Figure 17 shows two different types of the same circuit component.

What is the name of this circuit component?

Which row in the table describes the way that ammeters and voltmeters should be connected with a component in a circuit?

Figure 18 shows the results from an experiment where the potential difference (voltage) across a filament lamp was varied.

The current and voltage were measured.

Describe the relationship between the current and the voltage as shown in the graph in Figure 18.

Use the values of the voltage and current at point P and at point Q on the graph in Figure 18 to complete the table in Figure 19.

Calculate the resistance of the filament lamp when the voltage is 4.5 V and the current is 51 mA.

Use the equation

Explain why the resistance of the filament lamp changes as the voltage across it increases.

A technician investigates different electrical devices that are used in a car.

The technician connects a device to the 12 V car battery.

The technician measures the current in the circuit and the potential difference (voltage) across the device.

Figure 17 shows the car battery and the device that is being tested.

Draw on Figure 17 to show how the circuit should be completed so that the current in the circuit and voltage across the device can be measured.

The technician tests a headlamp.

The current in the headlamp is 4.8 A when connected to the 12 V battery.

Calculate the power supplied to the headlamp.

The technician tests an interior light.

The current in the interior light is 600 mA when connected to the 12 V battery.

Calculate the energy transferred to the interior light in 7 minutes.

Use an equation selected from the list of equations at the end of the paper.

The technician connects four devices to the car battery.

Each device is connected to its own switch and its own fuse.

Figure 18 shows how the four devices, fuses and switches are connected.

The current in each device is shown next to the device.

Calculate the current in the wires to the battery when all the devices are switched on.

State how the overall resistance of the circuit changes when any one of the devices is switched off.

There is a current of 2.3 A in the radio when the radio is working correctly.

Which of these should the technician choose to protect the radio circuit?

Explain why the wires to the battery in a car are thicker than the wires that connect each device to its switch and its fuse.

Figure 4 shows the inside of a mains plug.

The mains plug has three safety features.

One of these safety features has been ticked in the table.

Put two more ticks in the table to show the other two safety features.

Figure 5 shows a charger for a car battery.

The meter on the battery charger shows the current supplied to a battery.

The meter on the battery charger is

The battery charger supplies a steady current of 2.5 A to the battery.

Calculate the charge flowing to the battery in 8 minutes.

Use the equation

charge = currenttime

The transformer in another battery charger has a primary coil and a secondary coil.

The voltage across the primary coil = 230 V.

The voltage across the secondary coil = 15 V.

The current in the secondary coil is 3.1 A.

Calculate the current in the primary coil.

Use the equation

Figure 1 gives the names of three atomic particles and some descriptions of the charge on the particles and their position in the atom.

Draw one straight line from each atomic particle to its correct description.

Figure 2 shows the junction of three wires, F, G and H, in a circuit. The current in wire F is 6.0 A. The current in wire G is 3.5 A.

Calculate the current in wire H.

A wire in a circuit carries a current of 0.9 A. Calculate the quantity of charge that flows through the wire in 50 s.

State the unit of charge with your answer.

Use the equation

charge = current × time

Which of these symbols is used to represent a thermistor in an electrical circuit?

A student investigates how the current in a lamp changes with the potential difference across the lamp.

The student uses the results to calculate the resistance of the lamp.

The results are shown in the table in Figure 17.

One value of resistance is missing from the table in Figure 17.

Calculate the value of resistance that is missing from the table.

missing resistance =_........ Ω

The student writes this conclusion:

‘The resistance of the lamp is directly proportional to the potential difference.’

Comment on the student’s conclusion. Use information from Figure 17 in your answer.

*(c) Figure 18 shows a battery connected to a filament lamp.

Explain, in terms of the movement of charged particles, how energy is transferred from the battery, through the lamp, to the surroundings.

A resistor is connected to a power supply.

The potential difference across the resistor is 6.0 V.

Which of these corresponds to a potential difference of 6.0 V?

The resistor remains connected for a period of time.

The current in the resistor is 200 mA.

A total charge of 42 C flows through the resistor.

Calculate, in minutes, the time taken for this amount of charge to flow through the resistor.

Calculate the total energy transferred by the 6.0 V power supply when a charge of 42 C flows through the resistor.

The resistor becomes warm while there is a current in it.

Explain why the resistor becomes warm.

Figure 16 shows a cardboard tube with a wire coming out from each end.

There are two 10 ohm resistors inside the cardboard tube.

A potential difference of 6.0 V is connected between P and Q.

There is a current of 1.2 A in the wires.

Deduce how the resistors have been arranged inside the cardboard tube.