Current Electricity Flashcards

1
Q

What is current electricity?

A

Electrical change on the move, carried by free electrons (negative electrons)

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2
Q

What is a complete circuit?

A

A continuous pathway between the terminals of a power supply.

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3
Q

Draw a resistor symbol

A

(Check notes)
Rectangle with a line sticking out each end

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4
Q

Draw a cell symbol

A

(Check notes)
A tall thin line on the left and a short thick line on the right.
Positive symbol on the left and negative on the right.

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5
Q

Draw a variable resistor (rheostat) symbol

A

(Check notes)
Resistor symbol with an arrow cutting diagonally through the top right corner

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6
Q

Draw a battery symbol.

A

(Check notes)
Multiple cell symbols next to each other.
The positive and negative sides are still labelled, but do not put them between each cell.

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7
Q

Draw a fuse symbol

A

(Check notes)
Resistor symbol but the line goes all the way through.

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8
Q

Draw a lamp symbol

A

(Check notes)
Circle with an X through it

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9
Q

Draw a switch symbol.

A

(Check notes)

Closed switch: line with two circles along it

Open switch: line with two circles along it, but the line between the two circles points up diagonally

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10
Q

Draw an ammeter symbol

A

(Check notes)
Circle with an A inside it

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11
Q

Draw a voltmeter symbol

A

(Check notes)
Circle with a V inside it

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12
Q

What is a conductor?

A

A material that allows a electrical current to pass through it.
E.g metals.

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13
Q

What is an insulator?

A

A material that doesn’t allow an electrical current to pass through it.
E.g non metals.

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14
Q

How do you calculate the voltage of a battery?

A

Add up the voltage of each cell inside it.

*note, if a cell faces another it should not be included.

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15
Q

What is current measured in?

A

Amperes (A)
Amps for short.

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16
Q

How do you measure current?

A

Using an Ammeter.

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17
Q

What symbol represents current in a circuit?

A

I

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18
Q

How does current vary in a series circuit?

A

It is the same at all points.

*Note, the current leaving the power supply always equals the current returning to it.

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19
Q

How does current vary in a parallel circuit?

A

It splits into each branch.

*note, the current leaving the power supply is still equal to the current returning to it.

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20
Q

What direction does conventional current flow?

A

From the positive terminal to the negative terminal.

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21
Q

What direction do electrons flow?

A

From the negative terminal to the positive terminal.

22
Q

What symbol represents time?

A

t

23
Q

What symbol represents charge?

A

Q

24
Q

What is electric charge measured in?

A

Coulombs (C)

25
Q

What is the definition of current?

A

Rate of flow of electric charge

26
Q

What is the pyramid used to calculate charge, current and time?

A

Q
I x t

27
Q

What is one coulomb?

A

That charge passing any point in a circuit when a steady current of 1 ampere flows for 1 second.

28
Q

What is one ampare?

A

That current flowing in a conductor when a charge of 1C flows past any point in one second.

29
Q

What is potential difference (p.d.)?

A

Voltage

Electrons will try to flow from the higher energy level to the lower one.

As the potential difference in the circuit increases (more cells) the energy gained by the electrons will increase and the current flow will increase as the electrons move faster.

30
Q

How can the voltage along a whole series circuit be calculated?

A

Adding together the p.d.’s across all components

(The p.d.’s are found using voltmeters)

31
Q

How does voltage vary across the components in a parallel circuit?

A

They are all equal.

32
Q

How is an ammeter connected to a circuit?

A

In series.

33
Q

How is a voltmeter connected to a cercuit?

A

In parallel.

34
Q

How would you investigate Ohm’s law with a piece of wire?

A

Set up a circuit containing a battery, a switch, an ammeter, a piece of wire, a volt meter, and a variable resistor.

By changing the setting on the variable resistor we can change the voltage across the wire and the current flowing through it.

Get six readings of V and I by adjusting the variable resistor, and draw a graph showing these results.

35
Q

What does Ohm’s law state?

A

Current is directly proportional to voltage provided the temperature remains constant.

36
Q

What triangle is used when calculating voltage, current and resistance?

A

V
I x R

37
Q

How do resistors work? Use a diagram.

A

Check ‘lattice of positive nuclei and negative electrons’ in notes

When electrons move along a wire, they collide with other electrons within the lattice. The more collisions there are, the higher the resistance. When the temperature increases in the lattice the particles vibrate more and more collisions occur.

38
Q

What is RT?

A

Total resistance.

39
Q

How do you calculate RT in a series circuit? (Provided the resistors are equal)

A

RT = R1 + R2 + R3 + …

40
Q

How do you calculate RT in a parallel circuit? (Provided resistors are equal)

A

When two equal resistors are added together in parallel their combined resistance is halved.

41
Q

How do you calculate RT when resistors are unequal?

A

1/RT = 1/R1 + 1/R2 + 1/R3 + …

OR (if there are only 2 resistors)

RT = R1 x R2/R1 + R2

42
Q

What is short circuiting?

A

When the current passes by a component to follow the path of least resistance.

E.g. in a series circuit containing a lamp, a piece of wire is connected between to points on either side of the lamp. The current goes through the wire instead of the lamp and the lamp goes out.

43
Q

What is the relationship between the number of resistors connected in parallel and the total resistance (RT)?

A

The more resistors connected in parallel the lower the RT

44
Q

What factors affect the resistance of a wire? How does it affect it?

A

The longer the wire the higher the resistance. This is directly proportional.

The thicker the wire the lower the resistance. This is directly proportional.

45
Q

What triangle is used when calculating power, energy and time?

A

E
P x t

46
Q

How do you calculate efficiency?

A

Power (out)
——————
Power (in)

47
Q

What triangle is used to calculate power, current and voltage?

A

P
I x V

48
Q

What triangle is used when calculating power, energy and time?

A

E
P x T

49
Q

How do you calculate energy?

A

Current x Voltage x Time

50
Q

What is direct current?

A

DC

Current whose direction is constant and unchanging. E.g. Battery (cell)

51
Q

What is alternating current?

A

AC

Current whose direction changes from one way then back repeatedly eg mains electricity.