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OCR PHYSICS > P5 - Electric Circuits > Flashcards

P5 - Electric Circuits Flashcards

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1
Q

Objects with like charges…

A

Repel each other

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2
Q

Objects with opposite charges…

A

Attract to one another

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3
Q

Electric current is…

A

The flow of charge

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4
Q

Electric current is measured in…

A

Amperes

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5
Q

In an electric circuit the metal conductors contain…

A

Many charges that are free to move

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6
Q

In metallic conductors an electric current is…

A

The movement of free elections that are present throughout such materials

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7
Q

In a metal conductor there are ______ free electrons free to move but in an insulator there are ______ free electrons free to move

A

Many, few

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8
Q

An ammeter should be connected in a ______ circuit

A

Series

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9
Q

When a circuit is made the battery causes these free charges to move but…

A

They are not used up and instead flow in a continuous loop

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10
Q

The larger the voltage in a given circuit…

A

The greater the current

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11
Q

Components…

A

Resist the flow of charge through them

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12
Q

The larger the resistance in a given circuit…

A

The smaller the current will be

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13
Q

Resistance of connecting wires is…

A

So small it can usually be ignored

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14
Q

When electric charge flows through a component, work is done by _________ and energy is transferred from it to the component

A

The power supply

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15
Q

Power is…

A

a measure of the rate at which electrical power supply transfers energy to an appliance or decide and/or its surroundings

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16
Q

Resistors get hotter when there is an electric current flowing through them which is caused by…

A

Collisions between the moving charges and ions in the wire

This heating effect makes a lamp filament hot enough to glow

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17
Q

LDR’s resistance ________ as the light intensity _________

A

Decreases, increases

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18
Q

Thermistors’ resistance ________ as temperature __________

A

Deceases, increases

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19
Q

Two+ resistors in a series have more resistance than one on its own because…

A

The battery has to move charges through both of them

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20
Q

Two+ resistors in a parallel circuit provide less total resistance than one on its own because…

A

They provide more paths for the charges to move along

21
Q

Ohms law…

A

Resistance=voltage/current

22
Q

Voltmeters should be attached in a _______ circuit

A

Parallel, to show the p.d between any two chosen points

23
Q

Voltage across a battery provides…

A

A measure of the ‘push’ of the battery on the charges in the circuit

24
Q

Ignoring resistance, if you increase the voltage across a component…

A

Current through the component will increase

25
Q

When two objects rub together…

A

They become charged because electrons are transferred from one to the other

26
Q

Added batteries in a series circuit mean…

A
  • The total p.d is the sum of their individual p.ds. Average cell has 1.5V so if cells are connected in the same direction a p.d of 3.0V but if in different directions 0V
  • more cells means more p.d produced across each component which means more current through each component as a result
27
Q

More batteries added in a parallel circuit…

A
  • Voltage remains the same
  • more current capacity because each battery has its own path to the circuit without the restriction presented by the internal resistance of the other battery. This does not necessarily mean current increases.
28
Q

When two or more components are a connected in a series to a battery…

A
  • the current throughout each component is the same
  • the p.d across each component is equal to the p.d of the battery
  • the p.d is largest across the component with the greatest resistance
  • the change in the resistance of one component will result in the change in the p.d across all components
29
Q

The p.d of each component in a series equal the p.d of the battery because…

A

The work done on each unit of charge by the battery must equal the work done by it on the circuit components

30
Q

The p.d is largest across the component with the greatest resistance in a series because…

A

More work is done by the charge moving through a large resistance than a small one

31
Q

When several components are connected in a parallel circuit the their potential differences are _______ to that of the battery

A

Equal

32
Q

When several components are connected in a parallel circuit the current through each component is ________

A

The same, as if it was the only component present

33
Q

When several components are connected in a parallel circuit the current is _______ across the component with the smallest resistance

A

Largest

34
Q

When several components are connected in a parallel circuit the current is largest across the component with the smallest resistance because…

A

The same battery voltage causes a larger current to flow bough a smaller resistance than a bigger one

35
Q

Generators produce mains electricity by…

A

A process called electromagnetic induction

36
Q

When a magnet is moving into a coil of wire…

A
  • A voltage is induced across the ends of the coil.
  • if a magnet is moving out of the coil or the other pole of the magnet is moving in then the voltage is induced in the opposite direction
  • When the ends of the coil are attached to a circuit a current will flow
37
Q

A changing magnetic field caused by changes in the current of one wire can…

A

Induce a voltage in a neighbouring coil

38
Q

A changing current in one coil of a transformer will cause…

A

A changing magnetic field in the iron core which in turn will induce an changing potential difference across the other transformer coil

39
Q

A transformer can…

A

Change the size of an alternating voltage

40
Q

The size of a voltage induced by a magnet rotating in a coil of wire can be increased by…

A
  • increasing the speed of the rotation of the magnet
  • increasing the strength of its magnetic field
  • increasing the no. of turns on the coil
  • placing an iron core inside the coil
41
Q

The induced voltage across the coil of an a.c generator…

A

Changes during each revolution of the magnet

42
Q

When the current is always in the same direction…

A

It is a direct current, such as in a battery

43
Q

____ is used as it is easier generate than _____ and is easier to distribute over long distances

A

A.c, d.c

44
Q

The mains supply is…

A

A.c and 230V

45
Q

A current carrying wire or coil can exert a force on…

A

A permanent magnet or on another current-carrying wire or coil nearby

46
Q

If a current-carrying wire is placed in a magnetic field whose lines are at right angles to the wire…

A

The current-carrying wire experiences a force at right angles to both the current direction and the lines of force of the field

47
Q

If a current-carrying wire is parallel to the lines of force of a magnetic field…

A

It experiences no force

48
Q

A motor effect can be used to…

A

Produce continuous rotation of the coil by using a commutator to ensure that the direction of the current in the coil is reversed at an appropriate point in each revolution

49
Q

Motors can be used in domestic devices such as…

A

DVD players and electric motor vehicles

OCR PHYSICS (3 decks)

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