Paper 1 - Electricity Flashcards

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1
Q

What is 1V?

A

1 joule per coulomb

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2
Q

Why does a current in a resistor result in the electrical transfer of energy and an increase in temperature?

A
  • Electrical energy is converted to thermal energy due to the resistance encountered by the moving electrons
  • Increases temperature of the resistor
  • Used in appliances where heat is the desired outcome
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3
Q

How do circuit breakers protect the device or user in domestic appliances?

A
  • Circuit breaker opens when too much current in being carried by the wire
  • Causes an open circuit
  • Current cannot flow through an open/broken circuit
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4
Q

How does earthing protect the device or user in domestic appliances?

A
  • Made of copper
  • Low resistance path to the ground
  • Connected to the casing of electrical devices
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5
Q

Why is current conserved at a junction in a circuit?

A
  • Principal of conservation of electric charge
  • At any point in a circuit, the number of electrons entering the junction must be equal to the number of electrons leaving the junction
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6
Q

How do fuses protect the device or user in domestic appliances?

A
  • Made of a substance with a lower boiling point
  • Will melt if a circuit is carrying too much charge
  • Melted fuse will break the circuit so current cannot flow
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7
Q

What is the relationship between power, current and voltage?

A

P = IV

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8
Q

What is the relationship between energy transferred, current, voltage and time?

A

E = ItV

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9
Q

What is the difference between a.c. and d.c.?

A
  • a.c. is main electricity being alternating current
  • d.c. is electricity from a cell or battery being direct current
  • a.c. is @50Hz so changes direction 50 times per second, d.c. does not
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10
Q

Why is a series circuit better for some appliances?

A

When it is ideal to have:

  • Same current everywhere
  • Shared voltage across components
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11
Q

Why is a parallel circuit better for some appliances?

A

When it is ideal to have:

  • Shared current across components
  • Same voltage everywhere
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12
Q

How does the current in a series circuit depend on the applied voltage and the number/nature of other components?

A
  • Ohms law - I = V / Rtotal
  • The current in a circuit is directly proportional to the voltage
  • The current in a circuit is inversely proportional to the total resistance
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13
Q

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

A
  • Increase in resistance = decrease in current
  • Decrease in resistance = increase in current
  • Current and resistance are inversely proportional
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14
Q

Describe the variation of resistance in LDR’s

A
  • Increase in light = decrease in resistance
  • Decrease in light = increase in resistance
  • Current and light are inversely proportional
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15
Q

Describe the variation of resistance in thermistors

A
  • Increase in temperature = decrease in resistance
  • Decrease in temperature = increase in resistance
  • Current and temperature are inversely proportional
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16
Q

What can lamps and LEDs be used for in a circuit?

A

Indicating the presence of current in a circuit

17
Q

What is the relationship between voltage, current and resistance?

A

V = IR

18
Q

What is the relationship between charge, current and time?

A

Q = It

19
Q

What is electrical current in solid metal conductors?

A

A flow of negatively charged electrons

20
Q

What is voltage?

A

The energy transferred per unit of charge passed

21
Q

How does double insulation protect the device or user in domestic appliances?

A
  • Used in appliances with plastic exteriors that do not have earthing
  • 2 layers of non-conductive materials
  • Only used to cover live parts
22
Q

How does insulation protect the device or user in domestic appliances?

A
  • Plastic or non-conductive material wrapped around all 3 wires
  • Used to protect the appliance or user if a wire comes loose
23
Q

How is the voltage across 2 components in parallel distributed?

A

The voltage is equal

24
Q

How is the voltage across 2 components in series distributed?

A

It is shared between them

25
Q

What is current?

A

The rate of flow of charge

26
Q

What is the relationship between energy transferred, charge and voltage?

A

E = QV

27
Q

How does voltage vary in wires?

A
  • Voltage increases with current
  • They are directly proportional
28
Q

How does voltage vary in resistors?

A
  • Voltage increases with current
  • They are directly proportional
29
Q

How does voltage vary in metal filament lamps?

A
  • As voltage increases, the current initially increases
  • But current increases at a faster rate due to the heating of the filament
30
Q

How does voltage vary in diodes?

A
  • When voltage exceeds Vf the voltage in a diode increases significantly
  • The increases in not linear, it is exponential
31
Q

Why does a lamp receiving more current mean that it is brighter?

A
  • because power = current × voltage
  • voltage is the same for all lamps
  • current is greatest