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Physics: P2 > P2.3 Currents in electrical circuits > Flashcards

P2.3 Currents in electrical circuits Flashcards

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1
Q

What is the electric current?

A

The flow of electric charge

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2
Q

The size of the electric current is the…

A

Rate of flow of electric charge

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3
Q

What is the equation for the size of a current?

A

Q
I = —–
t

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4
Q

What is the current measured in?

A

Amps, A

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5
Q

What is the charge measured in?

A

Coulombs, C

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6
Q

What does the I stand for?

A

Current

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7
Q

What does the Q stand for?

A

Charge

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8
Q

The voltage is also known as the…

A

Potential difference

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9
Q

What is the potential difference between two points in an electric circuit?

A

The work done (energy transferred) per coulomb of charge that passes between the points

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10
Q

What is the equation for potential difference?

A

W
V = ——
Q

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11
Q

What is potential difference measured in?

A

Volts

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12
Q

What is the work done measured in?

A

Joules

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13
Q

What does the W stand for?

A

Work done

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14
Q

What does the V stand for?

A

Potential difference / voltage

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15
Q

What are thermistors used for in circuits?

A

Temperature sensors in fire alarms for example

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16
Q

What are LDRs used for in circuits?

A

To detect light levels, e.g. automatic security lights

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17
Q

What are current-potential graphs used to show?

A

How the current through a component varies with the potential difference across it

18
Q

How can the resistance of a component be found?

A

By measuring the current through, and potential difference across, the component

19
Q

The current through a resistor (at a constant temperature) is directly proportional to…

A

The potential difference across the resistor

20
Q

What is the equation for calculating the current, potential difference or resistance?

A

V = I x R

21
Q

What is resistance measured in?

A

Ohms

22
Q

What does the R stand for?

A

Resistance

23
Q

What does the current through a component depend on?

A

Its resistance

24
Q

The greater the resistance…

A

The smaller the current for a given potential difference across the component

25
Q

What is the potential difference provide by cells connected in a series the sum of?

A

The potential difference of each cell (depending on the direction in which they are connected

26
Q

For components in a connected series, the total resistance is the…

A

Sum of the resistance of each component

27
Q

For components in a connected series, there is the same…

A

Current through each component

28
Q

For components in a connected series, the total potential difference of the supply is…

A

Shared between the components

29
Q

For components connected in parallel, the potential difference…

A

Across each component is the same

30
Q

For components connected in parallel, the total current through the whole circuit is the…

A

Sum of the currents through the separate components

31
Q

The resistance of a filament bulb increases as the…

A

Temperature of the filament increases

32
Q

When does an electron current flow?

A

When electrons move through the conductor

33
Q

What can happen to electrons when traveling through the conductor?

A

They can collide into the ions from the metal

34
Q

What does the collision of electrons and ions cause?

A

Resistance as it makes it much more difficult for the current to flow

35
Q

Why is the resistance of a long wire greater than the resistance of a shorter wire?

A

Because the electrons collide with the ions more often

36
Q

Why is the resistance of a thin wire greater than the resistance of a thicker wire

A

A thin wire has fewer electrons to carry the current

37
Q

The current of a diode flows in…

A

One direction only

38
Q

The diode has a very high resistance in…

A

The reverse direction of that which they travel

39
Q

An LED emits light when the current flows through it in…

A

The forward direction

40
Q

Why is there an increasing use of LEDs for lighting?

A

It requires a much smaller current and is therefore much cheaper

41
Q

The resistance of a light-dependant resistor (LDR) decreases as…

A

The light intensity increases

42
Q

The resistance of a thermistor decreases as…

A

The temperature increases

Physics: P2 (6 decks)

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