levo

Electricity and Circuits

Direct and alternating current

  • 2 things to know
  • Paper 6

Overview

Direct and alternating voltages and their traces against time, the frequency of an alternating voltage, batteries and wall sockets, direct current from cells and batteries, and devices such as laptops that need direct current.

What you need to know

Answer each one before you reveal it.

Your recallNot started
Key term

What is the difference between a direct voltage and an alternating voltage?

Key term

How can you tell from a voltage-time trace that a supply is alternating rather than direct?

Questions from this subtopic

Each one with the model answer underneath.

  1. 1

    What is the difference between a direct voltage and an alternating voltage?

    Model answer

    A direct voltage keeps the same sign all the time, while an alternating voltage repeatedly reverses between positive and negative.

  2. 2

    Describe the shape of a trace of a direct voltage plotted against time.

    Model answer

    It is a horizontal straight line at a steady value on one side of zero.

  3. 3

    Describe the shape of a trace of an alternating mains voltage plotted against time.

    Model answer

    It is a repeating wave that rises and falls, crossing zero and reversing regularly.

  4. 4

    How can you tell from a voltage-time trace that a supply is alternating rather than direct?

    Model answer

    The trace of an alternating supply goes both above and below zero, while the trace of a direct supply stays on one side of zero.

  5. 5

    What does the frequency of an alternating voltage tell you?

    Model answer

    It tells you how many complete cycles the voltage goes through each second.

  6. 6

    Which type of voltage does a battery provide, and which type does a wall socket provide?

    Model answer

    A battery provides a direct voltage and a wall socket provides an alternating voltage.

Other ways to work this

The same content, four other ways.

What is inside Levo

Six ways to work the same material.

1Closed book
2Open book
3Closed book

The 3-step method, run for you

Answer cold, learn it, then prove it stuck. Levo tracks the jump between your first attempt and your last.

Key Concepts of Physics
Motion and Forces
Conservation of Energy
Waves

Cram a whole paper in one sitting

Sort every topic into what you know and what you do not, then drill only the weak ones.

2.5 × = 9000 s.
360027001000

Blank Blitz makes facts automatic

Rapid timed gap-fills on the terms and numbers you need to recall without thinking.

ALength is measured in metres, with the symbol m.
BMass is measured in kilograms, symbol kg.
CTime is measured in seconds, symbol s.

Build It gets the exam shape right

Assemble a full-mark answer from its marking points, in the order an examiner wants them.

Watt means the unit of power, symbol W.
TrueFalse

Test It catches misconceptions

Spot the fault in a statement. The traps are the mistakes students actually make.

721941163128510

Brain Breaks between sessions

Short focus games to reset attention, so the next set lands better than the last.

Every question in Electricity and Circuits, on a schedule.

Attempt a question from memory, write the correct version, then attempt it again. Levo records the jump between your first attempt and your last, and brings each question back on the day you are due to forget it.

Or £46 a year, about £3.83 a month. Cancel anytime.