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Physics > Electricity > Flashcards

Electricity Flashcards

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1
Q

Electric current

A

Is a flow of electrical charge (electrons).

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2
Q

When will electrical charge flow?

A

Only when the circuit is closed, so there is a potential difference. The unit for current is ampere A.

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3
Q

Potential difference

A

1 volt tells us that 1 j of energy is transferred for each coulomb of charge that moves through the circuit.

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4
Q

Resistance

A

Electrons collide with atoms in the conductor, energy is transferred to other stores such as thermal. Unit ohm

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5
Q

The current flowing through a component depends on the…..

A

Potential difference across it and the resistance of the component.

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6
Q

The greater the resistance across a component…

A

The smaller the current that flows.

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7
Q

The size of the current is the…

A 
Rate of flow of charge. 
Charge flow(Q)= current(l) x t(time, seconds)
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8
Q

More charge passes around the circuit when a…

A

Larger current flows.

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9
Q

Formula for potential difference

A

Potential difference(V)= Current(A) x Resistance(ohm)

V=IR

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10
Q

The ammeter

A

Measure the current in amps flowing through the test wire. Must be placed in series

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11
Q

The resistance of ohmic conductors(e.g. wire or resistor)…

A

doesn’t change with the current. At a constant temperature, the current flowing through is directly proportional to the potential difference across it.

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12
Q

The resistance of some resistors and components….

A

Does change (diode or filament lamp)

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13
Q

Filament lamp

A

Some energy is transferred the thermal energy store of the filament, which is designed to heat up. Resistance increase with temperature, so as the current increases, the resistance increases also.

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14
Q

Diodes

A

Resistance depends on the direction of the current. In reverse direction the resistance is very high.

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15
Q

LDR

A

Light dependent resistor. The resistance depends on the intensity of light. In bright light the resistance falls in darkness the resistance is highest.

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16
Q

Uses of LDR

A

Automatic night lights, outdoor lighting and burglar detectors.

17
Q

Thermistor

A

Is a temperature dependent resistor. In hot conditions the resistance drops in cool conditions the resistance goes up.

18
Q

Uses of thermistor

A

Useful temperature detectors, such as car engine temperature sensors and electronic thermostats.

19
Q

If you remove one component in a series circuit….

A

The circuit is broken and all the components stop.

20
Q

Potential difference in series circuit

A

The total pd of the supply is shared between various components. The pd round a series circuit always add up to equal the source pd.

21
Q

Current in the series circuit

A

The current is the same in all components. Current is determined by total pd divided by total resistance.

22
Q

Resistance in series circuit

A

Total resistance is sum of the resistance of all the components. Because by adding a resistor, two resistors have to share the total pd.

23
Q

(Series circuit) The pd accord each resistor is lower, so the current…

A

Through each resistor is also lower. In s. circuit current is the same everywhere so the total current in the circuit is reduced.

24
Q

(Series) The bigger a component’s resistance…

A

the bigger its share of the total pd is.

25
Q

Cell potential difference add up

A

There is a bigger pd when more cells are in series, if they are all connected the same way.

26
Q

If you remove one of the components…

A

it will hardly affect the others at all.

27
Q

(Parallel) Potential difference is….

A

the same across all the components.

28
Q

(Parallel) Current is…

A

shared between branches.

29
Q

(Parallel) Adding a resistor…

A

reduces the total resistance.

30
Q

The current flows from…

A

negative end of the cell to the positive end. However, it is drawn opposite direction.

31
Q

Electrons are carrying….

A

energy from the cell and pass the energy to the components in circuit such as lamp.

32
Q

When electrons return to…

A

the positive end of the cell, they are carrying less energy than when they left the negative end.

33
Q

Series circuit properties

A
  • convectional current
  • no branches
  • current can flows only in one path
  • current is always the same all the way around
34
Q

Electrical charge is measured in….

A

coulombs(c)

Current of 1 A = 1 c of charge flowing per second.

35
Q

The cell has a store of…

A

chemical energy, transferred to electrical energy carried by electrons.

36
Q

Battery

A

Two or more cells are connected together.

37
Q

Resistance tells the…

A

p.d. required to drive a current through component.

Physics (21 decks)

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