Electrical charge & current

This question is about electrical circuits.

The table shows the circuit symbols for some electrical components.

Complete the table by placing ticks (✓) to show whether each component can visibly indicate the presence of a current in a circuit.

Diagram 1 shows an electrical circuit containing a cell and component X.

The graph shows how the resistance of component X varies with temperature.

Give the name of component X.

Using the graph, determine the resistance of component X when its temperature is 50 °C.

The cell in diagram 1 has a voltage of 9.0 V.

Calculate the current in component X when its temperature is 50 °C.

Use the formula

voltage = current × resistance

The circuit in diagram 1 is modified by adding a second identical component X in series with the other components.

The temperatures of the first component X and second component X are reduced to 26 °C.

Explain how the resistance of the circuit is affected by these changes.

The photograph shows a camper van with a solar panel on its roof. The solar panel is made from lots of solar cells connected together.

The solar panel is connected to a battery. The solar panel receives energy from the Sun to charge the battery.

Describe how energy is transferred from the Sun’s energy store to the battery’s energy store.

The petrol engine can also be used to charge the battery of the camper van.

Give an advantage of using the solar panel instead of the petrol engine to charge the battery.

Do not refer to cost in your answer.

The surface of the solar panel is black.

Explain why black is a suitable colour for the solar panel.

The solar panel can charge the battery in the camper van with a maximum current of 15 A.

Calculate the minimum time to transfer 360 000 C of charge through the battery.

Use the formula

charge transferred = current × time

The diagram shows a rod and a cloth.

When the rod is rubbed with the cloth, the cloth becomes positively charged and the rod becomes negatively charged.

Explain how the cloth has become positively charged.

The negatively charged rod makes contact with a metal object connected to the ground.

There is an ammeter in series with the object and the ground.

Explain why the ammeter shows a current for a short time and then shows no current.

State the formula linking charge transferred, current and time.

The mean current displayed on the ammeter is 6.8 × 10^–6A.

The current lasts for 3.7 ms.

Calculate the charge transferred.

The diagram shows a domestic lighting circuit.

Explain an advantage of using this circuit for domestic lighting.

When switch 1 is closed, the current in lamp 1 is 22 mA.

Give the name of the charged particle that moves in an electric current.

Show that lamp 1 has a power of about 5 W.

Calculate the energy transferred by lamp 1 when it is on for 30 seconds.

The circuit is connected to the mains supply. Mains voltage is 230 V.

State what is meant by the term voltage.

Switches 1 and 3 are closed, which turn on lamps 1 and 3.

Switch 2 is open.

Calculate the current in the mains supply.

The photograph shows a power bank used to recharge the battery in an electronic device.

The power bank stores charge.

The charge stored can be measured in amp-hours (Ah). 1 Ah is the amount of charge transferred by a current of 1 A in a time of 1 hour.

Calculate the charge stored in coulombs when the charge stored is 1 Ah.

Use the formula

charge stored = current × time taken

An electronic device is connected to the power bank.

Whilst recharging, the electronic device receives a constant current of 2.4 A and 3.8 × 10³C of charge is transferred.

Calculate the time taken to recharge the electronic device.

Give your answer in minutes.

The electronic device is connected to the power bank using a long cable.

Suggest how using a long cable affects the time taken to recharge the electronic device when compared with a short cable.

A student owns three electronic devices. Each electronic device stores a different amount of charge.

The table gives some information about the charge stored by the electronic devices and how often they need to be recharged.

The power bank stores a maximum charge of 26.8 Ah.

The student needs to take these three electronic devices on a school trip for one week.

Determine whether the maximum charge of the power bank is enough to recharge the batteries of the three electronic devices during the school trip.

A student uses the circuit shown in diagram 1 to investigate how the current changes with voltage for a filament lamp.

Give the name of component Y.

Give a reason why component Y is included in the circuit.

The graph shows some of the student’s results.

State the formula linking charge, current and time.

Determine the current in the lamp when the voltage across the lamp is 10 V.

Calculate the charge transferred through the lamp in 30 s when the voltage across the lamp is 10 V.

Give the unit.

Calculate the time for the lamp to transfer 250 J of energy when the voltage across the lamp is 10 V.

The student disconnects the cell and reconnects it with its terminals reversed.

Complete the graph to show how the current in the lamp varies with voltage across the lamp when the cell is connected with its terminals reversed.

The student replaces the filament lamp with a light emitting diode (LED) and replaces the cell with an alternating current (a.c.) power supply, as shown in diagram 2.

The student also removes the ammeter and voltmeter from the circuit.

Explain why the LED flashes on and off in this circuit.

A tumble dryer is a household device that dries clothes.

The clothes rotate in a heated cylinder.

Clothes often stick together when they are dry because they become electrostatically charged.

A student investigates how different materials charge electrostatically in a model tumble dryer.

The diagram shows the model tumble dryer.

This is the student’s method.

• put four dry squares of the same material into the cylinder

• rotate the cylinder at constant speed for three minutes

• remove any squares that are stuck together

• measure the force needed to pull the squares apart

• repeat this for squares of different material

Name a device the student could use to measure a force.

State the independent and dependent variables in this investigation.

State a control variable in this investigation.

Explain how the squares of material stick together.

Use ideas about electrostatic charge in your answer.

The table shows some of the student’s results.

Explain which type of graph is the most appropriate to present the results from this investigation.

State the formula linking charge, current and time.

When the squares of material are pulled apart there is a small spark.

There is a current of 4.310^–6A in the air for a time of 2.3×10^–3s.

Calculate the charge that is transferred.

State what is meant by the term electric current.

Diagram 1 shows an electric circuit used to test a fuse.

Give a reason why an LED is included in the circuit.

Add another component to the circuit in diagram 1 to measure the current in the fuse.

Diagram 2 shows a different electric circuit containing three different lamps.

Calculate the current I₁.

State the current I₂.¹

Explain which lamp is the brightest.²

Diagram 1 shows a trolley seen from above.

A copper rod is attached to the front of the trolley.

The rod is connected to a voltmeter fixed to the trolley.

Diagram 2 shows the path of the trolley, backwards and forwards through a very strong magnetic field directed into the page.

The shaded area shows the magnetic field.

A voltage is induced in the copper rod as the trolley moves through the magnetic field.

Explain why the sign of the voltmeter reading changes as the trolley moves backwards and forwards.

Give a reason why the magnitude of the induced voltage might change.

The voltmeter is replaced by a resistor.

A charge of 1.410^–4C flows in the resistor during a time of 0.78 s.

Calculate the mean current in the resistor.

The thermal energy store of the resistor increases by 2.310^–6J as energy is transferred to it electrically.

Calculate the mean voltage across the resistor when a charge of 1.410^–4C transfers this energy.

The diagram shows a circuit containing a cell, two switches and two resistors, R₁ and R₂.

A light emitting diode (LED) is represented using the symbol

Draw a LED on the circuit diagram that will indicate when there is a current in resistor R₁.

Both switches in the circuit are now closed.

Draw an ammeter on the circuit diagram that will measure the current in the cell.

The voltage across the cell is 4.5 V.

Explain how the voltage across R₂ compares with the voltage across the cell.

Switch 1 is now opened whilst switch 2 remains closed.

State the formula linking energy transferred, charge and voltage.

The voltage across the cell stays constant at 4.5 V.

Calculate the charge transferred through the cell when the cell transfers 4.1 J of energy.

A student investigates how the current in resistor R₂ varies with the voltage across it.

Describe how the circuit could be modified for the student to do this investigation.

Diagram 1 shows a machine used for demonstrating electrostatics.

When the handle is turned, the dome becomes positively charged.

In terms of electron movement, give a reason why the metal dome becomes positively charged.

When the handle is turned for 15 s the dome gains 0.50 J of energy in its electrostatic store as it becomes charged.

The voltage between the dome and the earth is 120 kV.

Calculate the mean charging current during this time.

The metal dome is discharged.

A thin metal case is then placed on top of the metal dome, as shown in Diagram 2.

When the handle is turned, the thin metal case moves upwards away from the dome.

Explain why the thin metal case starts to move upwards.

Explain why the metal case reaches a maximum height above the metal dome.

This question is about electric current.

State what is meant by the term electric current.

Give the name of the particles that flow if there is an electric current in a wire.

An electric heater contains wires that heat up when there is a current in the wires.

The electric heater has a power of 1.4 kW when connected to a mains voltage of 230 V.

State the formula linking power, current and voltage.

Calculate the current in the wires.

Explain why the current in the wires causes the temperature of the wires to increase.

The diagram shows part of a device used to demonstrate electrostatic charge.

Negatively charged water droplets fall into bucket A.

Describe how bucket A becomes negatively charged.

Explain why the negatively charged droplets spread out as they fall.

A droplet hits bucket A with a speed of 3.8 m/s.

Calculate the kinetic energy of the droplet when it hits bucket A.

The total charge stored in bucket A is –1.110^–10 C.

This charge passes through the air between the buckets in 9.2 × 10^–3 s, causing a spark between bucket A and bucket B.

Calculate the mean current between the buckets.

The spark transfers a charge of –1.110^–10 C.

The mean voltage between the buckets is 1.7 kV.

Calculate the energy transferred by the spark.

This question is about a demonstration to show the link between current and charge.

The diagram shows two metal plates, X and Y, with a metal ball moving between them.

The two metal plates have no charge before the power supply is connected.

When plate Y is connected to the positive terminal of the power supply, the plate becomes positively charged.

Explain how plate Y gains a positive charge.

The metal ball becomes positively charged when it touches plate Y.

The metal ball then moves away from plate Y towards plate X.

Explain why the metal ball moves away from plate Y.

Give a reason why the ball is made of metal.

When the metal ball moves away from plate Y to plate X, a charge of 5.1 × 10^-6 C is transferred.

State the formula linking charge transferred, current and time taken.

Calculate the current if the metal ball takes 0.45 seconds to travel from plate Y to plate X.

Suggest why the current increases if the voltage of the power supply is increased.

Give the name of the apparatus that can be used to measure current.

This question is about electric circuits.

Which quantity is defined as the rate of flow of charge?

Which quantity is defined as the energy transferred per unit charge passed?

Diagram 1 shows an electric circuit with two resistors, R and S.

Some of the values of the current are also shown.

Diagram 1

On Diagram 1, draw a voltmeter to measure the voltage of resistor S.

Deduce the readings on the ammeters.

Resistor R has a resistance of 11 Ω.

Calculate the voltage across resistor R.

Explain how the voltage across resistor R compares with the voltage across the battery.

Diagram 2 shows a different circuit containing a battery, an ammeter and a thermistor.

Explain how the thermistor can be used to vary the current in this circuit.

A student uses this apparatus to demonstrate the effect of electric charge.

He pours some fine powder into a funnel.

The fine powder moves through a length of plastic tubing and falls into a metal can.

The metal can rests on a metal cap.

The metal cap is connected to a thin piece of metal via a metal rod.

When the powder lands in the can, the thin piece of metal moves away from the metal rod.

Explain why the thin piece of metal moves away from the metal rod.

A coulombmeter measures electric charge.

The student connects a coulombmeter to the metal can.

When all the powder has landed in the can, the coulombmeter shows a reading of –9.410^–9 C.

Which statement is true for the metal can?

State the formula linking charge, current and time.

It takes a time of 12 s from when the powder starts landing in the metal can until all the powder has landed in the can.

Calculate the mean charging current.

Give your answer to 2 significant figures.