P4.2 - current/charge/volatge/resistance Flashcards

1
Q

electric current

A

-flow of charge
-more electron flow per sec = bigger current

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2
Q

size of current =

A

rate of flow of charge
or charge per sec

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3
Q

electric charge unit

A

coulombs C

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4
Q

Current unit

A

amperes A

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5
Q

1 amp = how many c

A

1C per sec

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6
Q

equation for charge flow, current, time

A

charge = current x time

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7
Q

conventional flow

A

-positive to negative

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8
Q

electron flow

A

-negative to positive

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9
Q

Components of a circuit: cell

A

-pushes electrons around circuit

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10
Q

Components of a circuit: battery

A

2 or more cells

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11
Q

Components of a circuit: switch

A

-enables current to turned on/off

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12
Q

Components of a circuit: lamp

A

-emits light when current passes through

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13
Q

Components of a circuit: diode

A

allows current through one direction only

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14
Q

Components of a circuit: LED (light-emitting diode)

A

emits light when current passes the right way

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15
Q

Components of a circuit: ammeter

A

measures current

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16
Q

Components of a circuit: fixed resistor

A

limits current in a circuit

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17
Q

Components of a circuit: variable resistor

A

allows current to be varied

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18
Q

Components of a circuit: fuse

A

melts and breaks circuit if current it too big
-safety mechanism

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19
Q

Components of a circuit: heater

A

-transfer energy from current to heat surroundings

20
Q

Components of a circuit: voltmeter

A

measures P.D / voltage
Has to be parallel to the thing it’s measuring

21
Q

potential difference

A

-energy transferred to component that passes through it

22
Q

equation involving pd/energy/charge

A

P.D = energy transferred/charge

23
Q

resistance

A

-electrons passing through components have to push their way through lots of vibrating atoms
=resistance

24
Q

equation involving resistance/voltage/current

A

R=V/I

25
Q

unit for resistance

A

ohms

26
Q

larger resistance .. =

A

lower current

27
Q

ohms’ law states

A

-current passing through the resistor at a constant temp
-is directly proportional to PD of resistor

28
Q

ohmic conductor

A

resistance stays constant as current changes
-when temp is constant = obeys ohms law

29
Q

reversing pd across resistor =

A

reverses current

30
Q

non ohmic conductor eg

A

filament lamp
diode

31
Q

non ohmic conductor - filament lamp

A

-resistance isn’t constant
-charge depends on current
-not proportional
-higher current = more resistance as temp increases

32
Q

non ohmic conductor - diode

A

-low resistance in forward direction
-high resistance in the reverse direction

33
Q

ohmic conductor IV graph

A

-straight line
-goes through origin
- directly proportional

34
Q

non ohmic conductor - filament lamp

A

-curved line
-not proportional

35
Q

non ohmic conductor - diode

A

-forward direction line curves towards y axis
-reverse direction current = 0

36
Q

thermistors

A

temp dependent resistor
-resistance decreases if temp increases

37
Q

LED

A

-decreases resistance if the light intensity increases

38
Q

series circuits

A

consist of one loop of wire

39
Q

current in series circuits

A

-same current through each component

40
Q

series circuits - PD

A

-total pd is shared between components

41
Q

series circuits - resistance

A

-total R = R1+R2

42
Q

Parallel circuits

A

consists of 2 or more loops of wire

43
Q

Parallel circuits - pd

A

-pd is same across all components

44
Q

Parallel circuits - current

A

-total current = sum of current through components on each loop

45
Q

Parallel circuits - resistance

A

-total resistance is less than the resistance of the smallest resistor
-1/R1 + 1/R2 = Rt

46
Q

Light dependent resister or LDR

A

High light intensity - low resistance