The transformer

A transformer is made from two coils wound around a metallic core. What kind of voltage is provided to the transformer, and which metal is used to construct the core?

May/June 2015

A transformer and a diode are employed to charge a battery. Fig. 8.1 illustrates the transformer, which has a soft-iron core and two coils. The primary coil is joined to the 240 V a.c. mains supply. The secondary coil is connected in series with the diode and the battery.

May/June 2016

A student employs a transformer to power a filament lamp from a $230\,\text{V}$ a.c. supply. The lamp is rated for a maximum voltage of $6.0\,\text{V}$. What happens when the circuit is switched on?

May/June 2017

What material is used to make the core of a transformer?

May/June 2017

A step-down transformer contains a primary coil and a secondary coil wrapped around a soft-iron core. The primary coil is linked to a $6.0\,\text{V}$ direct current (d.c.) supply. Which statement about the transformer is correct?

May/June 2018

Fig. 8.1 depicts a transformer that links an overhead $25\,000\,\text{V}$ power line to a house.

May/June 2018

A student uses a transformer to power a filament lamp from a $230\text{ V}$ a.c. supply. The lamp’s maximum voltage rating is $6.0\text{ V}$. What occurs when the circuit is switched on?

May/June 2021

A student uses a transformer to power a filament lamp from a $230\,\text{V}$ a.c. supply. The lamp’s maximum voltage rating is $6.0\,\text{V}$. What occurs when the circuit is switched on?

May/June 2021

The diagram represents a model power-line circuit that includes two transformers and a lamp at the output. What is the voltage at the input?

May/June 2022

Fig. 8.1 illustrates a step-down transformer that is used to run an electric bell.

May/June 2023

A step-down transformer converts $240\,\text{V}$ a.c. into $12\,\text{V}$ a.c. The primary coil has $600$ turns. How many turns does the secondary coil have?

May/June 2024

The diagram depicts a transformer. A student records four statements about the way the transformer operates. 1. An alternating voltage across the primary coil leads to an unchanging voltage across the secondary coil. 2. An alternating voltage across the primary coil creates a changing magnetic field in the iron core. 3. A changing magnetic field in the iron core leads to an alternating voltage across the secondary coil. 4. An unchanging voltage across the primary coil creates a changing magnetic field across the secondary coil. Which statements describe how the transformer works?

May/June 2024

A step-up transformer is placed between a power station and a long-distance electricity transmission cable. What is the role of the step-up transformer, and does it work with alternating current (a.c.) or with direct current (d.c.)?

May/June 2025

A transformer is being used to supply a lamp. The secondary coil has more turns than the primary coil. Which statement is correct?

May/June 2025

Fig. 7.1 depicts an a.c. power supply linked to a transformer.

May/June 2025

Electric power cables carry electrical energy across long distances by means of high-voltage alternating current. What advantages are there in using a high voltage and in using an alternating current?

Oct/Nov 2015

Electric power cables carry electrical energy across long distances by using high-voltage, alternating current. What advantages come from using a high voltage and from using an alternating current?

Oct/Nov 2015

In the diagram, electrical device X is connected between a $6\,\text{V}$ a.c. supply and a $12\,\text{V}$ lamp. The lamp is observed to shine at normal brightness. What is X?

Oct/Nov 2015

Which material is most appropriate for the core of a transformer and which material is most appropriate for the coils in the transformer?

Oct/Nov 2016

The primary coil of a transformer is linked to the $230\,\text{V}$ a.c. mains supply.

Oct/Nov 2016

A $12\,\text{V}$ lamp shines at its normal brightness when it is connected to the secondary winding of a mains transformer. The mains voltage is $240\,\text{V}$. The transformer has an efficiency of $100\%$ and the primary winding contains $200$ turns. How many turns does the secondary winding have?

Oct/Nov 2018

Which row indicates the way in which the electrical energy generated by a power station is sent to towns far away?

Oct/Nov 2018

A transformer has an input voltage of $24\ \text{V a.c.}$ and an output voltage of $6.0\ \text{V}$. The input coil has $720$ turns. How many turns are there on the output coil?

Oct/Nov 2019

Transformers are employed to pass electrical energy from power stations into transmission cables, as illustrated. What role does the transformer shown in the diagram play?

Oct/Nov 2019

A transformer contains $4800$ turns on the primary coil and $480$ turns on the secondary coil. The primary coil is linked to a $240\ \text{V}$ a.c. supply, and the secondary coil is attached to a lamp. How does the current in the lamp at the output compare with the input current?

Oct/Nov 2020

For electricity sent over long distances, a transformer is first used to raise the voltage before transmission. At the far end, a second transformer lowers the voltage back to the normal mains value.

Oct/Nov 2020

A transformer working at an efficiency of $100\%$ has a primary voltage input of $600\,\text{V}$ and a secondary voltage output of $240\,\text{V}$. A resistor with resistance $120\,\Omega$ is connected to the secondary coil. What is the power dissipated in the resistor and what is the current in the primary coil?

Oct/Nov 2021

A transformer with $100\%$ efficiency has a primary voltage input of $600\,\text{V}$ and a secondary voltage output of $240\,\text{V}$. The secondary coil is connected to a resistor with resistance $120\,\Omega$. What is the power dissipated in the resistor and what is the current in the primary coil?

Oct/Nov 2021

Which statement concerning a transformer is correct?

Oct/Nov 2022

Which statement concerning a transformer is correct?

Oct/Nov 2022

The transformer’s primary coil is joined to the mains supply. The a.c. mains voltage is 240 V. Fig. 6.1 shows the layout.

Oct/Nov 2022

In a mobile phone (cellphone) charger, a transformer is used to step the voltage down from $230\,\text{V}$ to $5.0\,\text{V}$. The primary coil of the transformer has $2500$ turns. How many turns are on the secondary coil?

Oct/Nov 2023

A girl constructs a simple transformer to light a low voltage lamp. The transformer is illustrated. What is the rod made of, and what type of power supply is used?

Oct/Nov 2023

An alternating current mains electricity supply has a frequency of 50 Hz, and its maximum voltage is 300 V.

Oct/Nov 2024

A student is using a simple transformer with an iron core. The primary coil contains 250 turns, while the secondary coil contains 200 turns. The voltage supplied to the primary coil is $12\,\text{V}$. What is the output voltage?

Oct/Nov 2025