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Physics > P5 - Electric Circuits > Flashcards

P5 - Electric Circuits Flashcards

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1
Q

Like charges _____ and unlike charges _______

A

Like charges repel and unlike charges attract

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2
Q

Static is formed when two _______ rub together

A

Insulators

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3
Q

The object that loses electrons becomes ________ charged and the object that gains electrons becomes _______ charged

A 
Loses = positively charged
Gains = negatively charged
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4
Q

When you rub a polythene rod with a duster, which or the two items becomes negatively charged and why?

A

Rod = negative because electrons are transferred from the duster to the rod

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5
Q

Describe the electrostatic induction that occurs when a positively charged balloon approaches a wall: (3)

A

•when a positively charged balloon approaches a wall (neutral), the electrons in the wall are attracted to the surface, creating a negatively charged surface, attracting the balloon

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6
Q

Why do only electrons in an atom create charge and not protons too?

A

Electrons are free to move and protons are stuck in the nucleus; this is why in a wall during electro static induction, electrons can be attracted or repelled but protons can’t

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7
Q

Why are metals good conductors of electricity?

A

They have free electrons that can move and carry charge

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8
Q

What aren’t plastics good electrical conductors?

A

They don’t have as many free electrons as metals so charge cannot be carried effectively

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9
Q

Explain the flow of charge in an electrical circuit (3)

A
  • the cell (battery) provides energy for the electrons
  • in a complete circuit, there are free electrons in al the metal components so they carry the charge around the circuit
  • electrons carry negative charge so are attracted towards the positive terminal
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10
Q

What types of energy do bulbs produce? (2)

A

Heat and light energy

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11
Q

What is Electric Current and what units is it measured in?

A

The rate of flow of charge or the charge flowing per second; measured in amperes or Amps (A)

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12
Q

How many Amps is a Milliamp? (mA)

A

1 x 10^-3 of an amp or 1/1000 of an amp

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13
Q

What is the equation for charge, including units?

A

Charge/ Q (coulombs) = Current/ I (Amperes) x time/ t (seconds)

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14
Q

Voltage

A

The amount of energy needed to make the current flow

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15
Q

Ammeter: What is it? How is it connected?

A

A device used to measure current which is connected in series either side of a component

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16
Q

Voltmeter: What is it? How is it connected?

A

A device used to measure voltage which is connected in parallel to the bulb or a component

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17
Q

What is the unit of voltage?

A

Volts (V)

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18
Q

The larger the voltage, the _____ the current

A

The larger the voltage, the bigger the current

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19
Q

Power: what is it? What are the units?

A

Power is the rate at which energy is transferred and is measured in Watts (W)

20
Q

What is the equation for power?

A

Power = Voltage x Current

21
Q

What is potential difference

A

Another word for voltage; the different in energy per unit charge; a potential difference of 1 volt means that 1 joule of energy is transferred into or out of electrical form per unit of charge
OR
V = J/Q (energy in joules/ charge in coulombs)

22
Q

Static charge

A

A form of electric charge which does not move

23
Q

Resistance

A

A measure of how much a conductor opposes current

24
Q

What is the equation for resistance?

A

Resistance = voltage / current

25
Q

What is the equation of ohms law?

A

Voltage = resistance x current

26
Q

What type of resistors are light bulbs?

A

Non ohmic resistors

27
Q

The current is _____ through all components in s series circuit

A

The same

28
Q

Adding more bulbs in series does what to the resistance and the current?

A

It increases resistance and decreases the current

29
Q

In parallel the current is

A

Split between the different pathways

30
Q

Adding resistance in parallel

A

Reduces the total resistance

31
Q

With thermistors, the hotter the temperature, the ____ the resistance

A

Lower

32
Q

With LDRs, the brighter the light the ____ the resistance

A

Lower

33
Q

Magnetic field

A

The space around a magnet in which a magnetic force acts

34
Q

How do you increase the current induced by an electromagnet? 3

A

Increase the speed of motion
Use a stronger magnet
Have more turns in the coil

35
Q

How can you induce a larger voltage from a generator? 4

A

Use a stronger magnet
Increase the number of turns of wire
Use an iron core
Increase the rate of the coil being turned

36
Q

Alternating current

A

A current where every half term it changes direction

37
Q

Give an example of an object that uses direct current

A

Batteries

38
Q

What is the voltage and the frequent of the U.K. Mains?

A

230V 50Hz

39
Q

Why is the uk mains power a.c.? 2

A

It is easier to generate in large quantities and different fuels can be used in power stations

40
Q

Give 4 examples of objects which contain motors:

A

DVD/ CD players, washers and dryers

41
Q

Explain the motor effect; why does the wire turn in a motor?

A

When a current flows in a wore near a magnetic field, the wire experiences a force which is at its largest when the current is at right angles to the magnetic field lines

42
Q

How can you make a motor turn faster? 4

A

Increase the current
Increase the number of turns in the coil
Get a stronger magnet
Use a soft iron core

43
Q

Transformer

A

A component which changes the voltage of any ac power supply

44
Q

Do transformers work on alternating or direct current and why?

A

They only work with alternating as a changing magnetic field is needed to induce a voltage in the second coil

45
Q

How do you work out the efficiency of a power station? Equation

A

% efficiency = useful power out / power in x 100

46
Q

Why does the uk national grid transport electricity at high voltages? 2

A

They are good because high voltage means low current so less wasteful energy transferred and less damage to wires

47
Q

Why does we use the high voltages of the national grid in our homes?

A

Everything would melt and we would be killed :)

Physics (6 decks)

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