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Physics > Electricity > Flashcards

Electricity Flashcards

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1
Q

Relationship between power, current and voltage

A

P = I x V
Power (W) = current (A) x voltage (V)

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2
Q

Relationship between current, energy transferred, voltage and time

A

Energy transferred (J) = current (A) x voltage (V) x time (s)
E = I x V x t

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3
Q

relationship between resistance, current and voltage

A

Voltage (V)= current (A) x resistance (Ω)
V = I x R

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4
Q

relationship between current, charge and time

A

Charge (C) = current (A) x time (s)
Q = I x t

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5
Q

relationship between charge, voltage and energy transferred

A

energy transferred (J) = charge (C) x voltage (V)
E = Q x V

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6
Q

How does insulation and double insulation work?

A

Insulation
- wires are covered with an insulating material
- non-metallic case that acts as a second layer of insulation (double insulation)

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7
Q

How does earthing work?

A
  • Additional safety wire
  • earth wire links the casing to the energy source
  • when the live wire touches the casing, current flows through the casing and along the earth wire to complete the circuit
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8
Q

How do Fuses work?

A
  • safety device to cut off the flow of electricity when current becomes too large
  • usually a glass cylinder containing a thin metal wire
    When current is too large
  • wire melts, causing the wire to break and stopping the current
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9
Q

How do circuit breakers work?

A
  • automatic electromagnet switch that breaks the circuit when current exceeds
    + does not melt / break
    + reusable
    + fast
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10
Q

What is direct current?

A

Current that continuously flows in the same direction

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11
Q

What produces direct current?

A

Electric cells or batteries

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12
Q

What is alternating current?

A

Current that constantly changes direction

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13
Q

What kind of terminal does direct current have?

A

Positive and negative terminal

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14
Q

What kind of terminal does alternating current have?

A

2 identical terminals

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15
Q

What produces alternating current?

A

Electrical generators (main electricity)

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16
Q

Why does current in a resistor increase temperature?

A
  • When electricity passes through a resistor some of the electrical energy turns into heat
  • electrons collide with ions in the lattice that make up the resistor as they flow through, giving ion energy, causing it to vibrate and heat up
17
Q

2 advantages of a series circuit

A
  • All of the components can be controlled by a single switch
  • Fewer wires are required
18
Q

2 Disadvantages of a series circuit

A
  • Components cannot be controlled separately
  • If 1 component breaks the rest will stop working as well
19
Q

2 advantages of a parallel circuit

A
  • Components can be individually controlled
  • If a component breaks, others will continue to function
20
Q

2 Disadvantages of a parallel circuit

A
  • More wires are required
  • All components have the same voltage as the supply, (harder to control if components need diff. voltages)
21
Q

What 2 things does the current in a series circuit depend on?

A
  • voltage of the power source
  • Number and type of components in the circuit
22
Q

What is the effect of changing resistance on the current in a circuit

A

As resistance increases, current decreases

23
Q

How does the resistance of LDRs change with light intensity?

A

As light intensity increases the resistance of an LDR decreases

24
Q

How does resistance of a thermistor change depending on temperature?

A

As temperature increases the resistance of a thermistor decreases

25
Q

What does adding lamps or LEDs to a circuit indicate?

A

Presence of a current

26
Q

What is current

A

the rate of flow of charge

27
Q

What does current do at a junction?

A

Current ‘splits’ to take both paths.
It comes back together when the paths meet again.
e.g - I1 = I2 + I3 +I4

28
Q

What happens to voltage across 2 components connected in parallel

A

The voltage is equal
VT = V1 = V2

29
Q

How do you calculate the currents of 2 resistive components connected in a series circuit

A

IT = I1 = I2

30
Q

How do you calculate the voltage of 2 resistive components connected in a series circuit

A

VT = V1 + V2

31
Q

How do you calculate the resistances of 2 resistive components connected in a series circuit

A

RT = R1 + R2

32
Q

what is voltage

A

voltage is energy transferred per unit charge passed
V = energy transferred (J) / charge (C)

Physics (5 decks)

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