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GCSE- Physics > Topic 10- Electricity and Circuits > Flashcards

Topic 10- Electricity and Circuits Flashcards

1
Q

What is potential difference?

A
  • Diference of potential electrical between two points
  • How much (energy) is used in a component
  • Energy carried by electrons
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2
Q

What is current?

A

-Flow of electrons
- From positive to negetive…

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3
Q

What is a volt in coulombs?

A

Joule/coulomb
- potential difference is how much energy transfered per unit of charge/ current

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4
Q

Charge =

A

Current x time

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5
Q

Energy =

A

charge x potential difference

number of electrons x how much energy transferred to components

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6
Q

Why does potential difference cuase flow of electrons

A
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7
Q

where is current conserved?

A

current is conserved at a junction in a circuit

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8
Q

What does a variable resistor work?

A
  • Lengthens wire and increases resistance
  • Decreases current
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9
Q

Voltage =

A

Resistance x Current

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10
Q

What is current measured in?

A

-I
-Amps

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11
Q

What is Voltage measured in?

A

-V
-Volts

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12
Q

What is charge measured in?

A

-Q
-Coulumbs

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13
Q

What is energy measured in?

A

-E
-Watts

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14
Q

What is resistance measured in?

A

-Ω
-Ohms

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15
Q

Potential difference series?

A
  • Split
  • All components only have enough energy as batterty
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16
Q

Current series?

A
  • Same everywhere
  • Only one way electrons can flow
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17
Q

Resistance series?

A
  • Added together
  • One electron flow so all encounter same resistance
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18
Q

Potential difference parallel?

A

-Same everywhere
- Current and resistance are indirectly proportional, keeping voltage the same

-choose path of least resistance
-But more electron flow cuases higher resitance
-so overall less r and more I
-or more r and less I
-V= IR

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19
Q

Current parallel?

A
  • Different
  • They choose path of least resistance
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20
Q

Resistance parallel?

A
  • Different, cannot add
  • 1/R1 + 1/R2 + 1/R3

-Cuase not all resistance is in the same route

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21
Q

Why does net resistance decrease in parallel?

A
  • Adding another pathway for electrons
  • (3 resistors in series vs 3 resistors in parallel)
  • (electrons go through all 3 vs just one per route)
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22
Q

Core Practical: Construct electrical circuits to:

a) investigate the relationship between potential difference, current and resistance for a resistor and a filament lamp

A

1) Variable resistor: changes voltage by changing resistance

2)Ammeter: Take readings of current

3)Volmeter: Take reading of voltage across the fixed resistor

4) Fixed resistor: Investigate how higher volt supply changes current if resistance does not change

Independant: Voltage (variable resistor)
Dependant: Current
Control: Same components/fixed resistor and power supply

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23
Q

Core Practical: Construct electrical circuits to:
test series and parallel circuits using resistors and filament
lamps
RESULTS

A

-Attach 2 lamps in series with ammeter and volmeter
-Take readings
-Repeat in parallel circuit
* - Brighter in parallel as there are more routes for electrons and therefore less resistance

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24
Q

How does current vary with potential difference for a filiment lamp
relating to its resistance?

Describe graph and explain

A
  • slight S shape
  • When more V is supplied it is brighter and hotter
  • Heating effect cuases more resistance meaning less current
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25
Q

How does current vary with potential difference for a diodes
relating to its resistance?

A
  • Flat line and sudden rapid increase at 0.6-0.7 v
    -As Voltage increase
    -Resistance decreases rapidly
    -Causing current to rapidly increase
26
Q

How does current vary with potential difference for a fixed resistors
relating to its resistance?

A
  • Directly proportional
  • Resistance is fixed
27
Q

What is an ohmic conductor?

A

Current and voltage are directly proportional if temperature is constant

28
Q

How does resistance change with brightness of an LDR

A
  • Higher resistance when dimmer
  • Lower resistance when brighter
29
Q

How does resistance change with temperature of an thermister

A
  • Higher resistance when coldere
  • Lower resistance when hotter
30
Q

Experiment to find relationship witth volts and current of a resistor or filiment lamp:

A

-Battery: supply potential difference

-Ammeter: current

-Volmeter: across the resistor/ lamp

1) Note down readings

2) Variable resistor: changes resistence and therefore voltage

3) Reverse battery/ current for negative readings

31
Q

Experiment to find relationship with volts and current of a resistor: PROBLEM and SOLUTION

A
  • Get too hot/heating effect increase resistance
  • Don’t leave circuit on for too long
32
Q

Why do we use a fixed resistor in a circuit with a diode?

A
  • Diodes easily damaged by high current
  • extra resitor keeps current reletively low
33
Q

What and why do we use instead of an ammeter for diode experiment?

A
  • Miliammater (reads smaller currents)
  • Low current (extra reistor)
34
Q

Experiment to find relationship witth volts and current of a Diode:

Same as + what is extra

A
  • Same as resistor/ filiment lamp
  • Use extra resistor and a miliammeter
  • there will be no readings for reveresed current
35
Q

What is the heating effect?

A

Resistance cuases electrons to transfer energy in the form of heat

36
Q

How to reduce energy loss in circuits?

A
  • Low resistance wires
  • Insulate wires
37
Q

Why do hotter wires cuase higher reistance?

A

-Ions vibrate more
-More likely to collide with electrons

38
Q

Heating effect posisitves/ Uses?

A

-Kettle
-Domestic heating
-Electric ovens/ toasters

electrical work —> thormal store

39
Q

Heating effect disadvantages?

A
  • Energy loss
  • Fire hazard
40
Q

Energy =

current

A

Current x Time x Potential difference

E= I x t x V

41
Q

What is power

A

Rate of energy

Energy transferred per second

42
Q

Power=

A

Energy/ Time

P = E/T

43
Q

Power =

Current

A

Current x Potential difference

P = IV

44
Q

Power =

A

Current ^2 x resistance

P= I^2 x R

45
Q

Direct vs Alternating current: voltage

A

-Direct: voltage remains the same
-Alternating: Voltage switches between positive and negative

46
Q

What supplies + what is direct current?

A
  • Battery/ Cell
  • Current moves in one direction only
47
Q

What is an alternating current?

A
  • Charge movement changes direction
48
Q

Uk domestic supply: Curent, Hz and voltage

A
  • a.c (alternating)
  • 50Hz (alternates per second)
  • 230 V
49
Q

What does the live wire do?

A
  • Supplies alternating potential difference of about 230 volts
50
Q

Live wire colour?

A

Brown

50
Q

Neutral wire colour?

A

Blue

50
Q

Earth wire colour?

A

Green and yellow striped

51
Q

What does the neutral wire do?

A
  • Completes the circuit
  • Carries away current (out/ back into mains)
52
Q

Earth wire and Neutral wire potential difference

A

0 volts

53
Q

What does the Earth wire do?

A
  • Stops the casing from becoming live
  • By allowing an alternate pathway for the current to flow
54
Q

What are wires made of?

A

-Copper

55
Q

Why should a fuse and switch be attached to the live wire?

A
  • To break the connection to the mains supply (fuse melts due to too much current heating it up, as it has a low melting point)
  • Stop the casing becoming ‘live’
56
Q

Why is the earth pin longer?

A

-Connects with the socket first
-Provides alternative pathway incase live wire is broken

57
Q

What would happen if the live and Earth wire touched?

A
  • Direct circuit between the Earth and 230v
  • Could cause a fire or shock
58
Q

Which domestic electrical appliances have higher power ratings?

A

Thermal apliances (kettle/oven vs fan)

59
Q

What do power ratings show?

A

Energy it transfers/ work done per second

GCSE- Physics (8 decks)

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