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Electricity Flashcards

(52 cards)

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1
Q

What’s the symbol for a fuse?

A

Line passing through a rectangle

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2
Q

What’s the function of a fuse?

A

Breaks the circuit when current is too high.

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3
Q

What’s the symbol for a thermistor?

A

Rectangle with bent line accross.

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4
Q

What’s the symbol for a resistor?

A

Rectangle

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5
Q

What’s the function of a resistor?

A

Increases resistance to limit current

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6
Q

What’s the symbol for a variable resistor?

A

Rectangle with upwards diagonal arrow.

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7
Q

What’s the symbol for a diode?

A

Line passing through a circle with a triangle and line in the center.

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8
Q

What’s the function of a diode?

A

Makes current flow in one direction only.

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9
Q

What’s the symbol for a LED?

A

Line passing through a circle with a triangle and line in the center and two outwards facing arrows.

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10
Q

What’s the function of an LED?

A

Emits light when current passes through.

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11
Q

What’s the symbol for an LDR?

A

Circle with a rectangle and two arrows facing inwards.

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12
Q

Define current.

A

The rate of flow of charge (Amps)

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13
Q

In circuits, what is current?

A

Electrons flowing

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14
Q

Explain the current in metals that was believed initially.

A

Initially, it was believed positive charge flows from the positive to the negative terminal (conventional current), with metal ions adding resistance.

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15
Q

Define potential difference.

A

Work done per unit charge.

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16
Q

Now, what do we know about the flow of electrons?

A

After the discovery of the electron, its known that electrons flow from the negative to the positive terminals.

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17
Q

Define resistance.

A

Something that limits current (ohms)

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18
Q

What does higher resistance mean?

A

Lower current

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19
Q

Voltage= ?

A

Current x resistance

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20
Q

RP3: Explain how do to the practical of investigating resistance as the length of a wire changes.

A

By connecting two crocodile clips to wire at 10 cm apart and power supply 1.5 V, record the p.d. and current. Remove wire to cool. Move croc clips 10cm further, measure again. As length inc, resistance also inc.

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21
Q

What are the 2 types of resistors?

Study These Flashcards
A

Fixed- resistance stays the same.
Variable- Can change the amount of resistance.

22
Q

What does Ohm’s law state and which formula defines it?

Study These Flashcards
A

Current and Potential difference are directly proportional, V= IR because resistance remains constant.

23
Q

Give examples of Ohmic conductors.

Study These Flashcards
A

Wires, fixed resistors.

24
Q

What is meant by a non-Ohmic conductor?

Study These Flashcards
A

Current and Potential difference aren’t directly proportional, so resistance changes.

25
Give examples of non-Ohmic conductors.
Filament lamp, LDRs, thermistors
26
Why does resistance change in filament lamps?
Temperature increases, which provides kinetic energy to the particles in the lamp, causing them to vibrate more which makes it more difficult for current to pass. Reduced current means increased resistance.
27
What does a diode do, and what type of current- p.d. graph does it create?
Allows current to flow in one direction only as forward bias and has high levels of resistance for reverse bias. Graph: sharp increase as p.d. rises but at 0 before 0V.
28
What's the function of a thermistor?
Decreases resistance as temperature increases.
29
What are the applications of a thermistor?
Thermostats to display a reading, refrigerators and fire alarms.
30
What's the function of an LDR?
Decreases resistance as light intensity increases.
31
What are the applications of an LDR?
Street lights- when light intensity is low, resistance is high and current is low in the LDR and so is Voltage, which is shared in series. But voltage in the lamp is high, which means street lights are turned on.
32
RP4: To investigate how current in a resistor, diode and filament bulb are affected by voltage.
Set up apparatus w voltmeter and ammeter, inc voltage by 0.5V (use variable resistor) and record current. Switch off apparatus between readings. Replace resistor w diode then w filament bulb.
33
Describe series and parallel circuits.
Series- One loop, connected end to end. Parallel- Separate branches.
34
In series circuits.. current is...? voltage is...? Resistance is...?
Current=> SAME accross components Voltage=> SHARED across components Resistance=> R1+R2+R3= RT
35
In parallel circuits.. current is...? voltage is...? Resistance is...?
Current=> SHARED accross components Voltage=> SAME across components Resistance=> 1/R1+1/R2+1/R3= 1/RT and The total resistance of two resistors is less than the resistance of the smallest individual resistor
36
Define alternating current.
Current that is always changing direction (going back and forth) between 2 terminals
37
What is the frequency and potential difference of a.c?
50Hz and 230V
38
Define direct current.
A current that is steady, constantly flowing in the same direction in a circuit, from positive to negative
39
What does an oscilloscope do?
Displays the current.
40
What is mains electricity?
A.C generated by power stations and transported around the country through the National Grid
41
Name the 3 core cables in a plug and their colors.
Live wire- Brown (Right) Neutral- Blue (Left) Earth- Green/yellow (Top)
42
What are the functions of the 3 core cables?
Live- carries a.c. from mains to circuit, most dangerous. Neutral- Completes the circuit, low voltage Earth- safety wire, stops electrocutions
43
What are the dangers of mains electricity?
If the metal appliance comes in contact w the live wire, it will be electrified. To stop this, the earth wire provides a low-resistance pathway so a surge of current flows and causes a fuse to break the circuit.
44
Define power.
Rate at which energy is transferred.
45
Describe the energy transfer in a.c.
Mains--> Kinetic store in motor
46
Describe the energy transfer in d.c.
Chemical store in battery ---> Kinetic store in motor
47
What is a power rating?
How much energy is needed for an appliance to work. (Higher= more energy needed)
48
What is the National Grid responsible for?
Distributing electricity across the country via cables and transformers, linking power stations.
49
Explain the order of the National Grid.
Power station-- Step up transformer--- Pylons-- Step down transformer-- Homes
50
Explain the use of Step up/down transformers.
Step up: Increases the voltage, this decreases current so less thermal energy is lost bc pylons are cooler, this means higher efficiency. Step down transformers then decrease the voltage so its safer for consumers.
51
Do step-up transformers have more primary or secondary coils?
More secondary coils
52
Do step-down transformers have more primary or secondary coils?
More primary coils

Physics (6 decks)

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