Flashcards in Electricity - Paper 1 Deck (38)

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1

## Draw the circuit symbol for a lamp

### an X in a circle

2

## Draw the circuit symbol for a diode

### An arrow head in a circle

3

## Draw the circuit symbol for a resistor

### A rectangular box

4

## Draw the circuit symbol for a variable resistor

### A rectangular box with a diagonal arrow

5

## Draw the circuit symbol for an LED

### Same as a diode with 2 arrows points away

6

## Draw the circuit symbol for a fuse

### A rectangular box with a horizontal one running through it

7

## Draw the circuit symbol for a voltmeter

### V in a circle

8

## Draw the circuit symbol for an ammeter

### A in a circle

9

## Draw the circuit symbol for a thermistor

### a rectangular box with a diagonal line through it

10

## Draw the circuit symbol for an LDR

### A rectangular box in a circular with 2 arrows pointing towards it

11

## Define Current

### Flow of charge (electrons) measured in amps (A)

12

## State the equation that links charge, current and time.

###
Charge = Current x time

Q = It

13

## What are the units of charge

### Coulombs (C)

14

## What is the relationship between current and resistance?

### As resistance increases, current decreases and vice versa

15

## State the equation that links potential difference, current and resistance

###
Potential difference = Current x resistance

V = IR

16

## State the units of potential difference

### Volts (V)

17

## State the units of resistance

### Ohms

18

## State the relationship between the length of wire and its resistance.

### As the length of the wire increases the resistance increases. they are directly proportional

19

## As more resistors are added in series what happens to the total resistance.

### Total resistance increases (Rt = R1 + R2 + .....)

20

## State ohms law

### Current is directly proportional to potential difference constant temperature. this means resistance remains constant.

21

## Sketch the I/V graph for a resistor

### A straight line through the origin (current and potential difference are directly proportional - an ohmic conductor)

22

## Sketch the I/V graph for a bulb

### It starts off as a straight line through the origin but the the current levels offs so the graph curves. Non ohmic conductor

23

## How does the resistance of a lamp change as it heats up?

### As temperature increases resistance increase. Atoms/ions have more energy so vibrate more taking up more space making it harder for electrons to travel down the wire.

24

## Sketch the I/V graph for a diode

### Current can only flow in one directions. So zero current in the negative direction but in the positive direction current increases slightly after the origin. Non ohmic conductor

25

## State the relationship between temperature and resistance for a thermistor

### As temperature increases resistance decreases.

26

## State some uses of thermistors

### In thermostats to turn circuits on/off if they get too hot to cold e.g. in an iron, hair straighteners etc

27

## State the relationship between temperature and light intensity for a LDR

### As light increases increases, resistance decreases

28

## State some uses of LDRs

### In circuits to switch lights on when it gets dark

29

## state the rules for current, potential difference and resistance in a series circuit

###
Current - same flowing through each component

Potential difference - the p.d. of the power supply is shared between the other components

Resistance - the total resistance increases as more components are added. the total resistance is the sum of all the individual components resistance

30

## state the rules for current, potential difference and resistance in a parallel circuit

###
current - splits up but the total current stays the same

Potential difference - across each brach is the same as from the battery

Resistance - decreases as more branches are added. the electrons have more choice of paths to take.

31

## What happens when electrical current flows through a resistor?

### Electrical energy is transformed into heat energy

32

## What is a short circuit?

### An electrical circuit that allows current to travel along unintended paths with no or very low resistance Resistance low = current very high. This will cause the battery to overheat

33

## Why do lamps blow when they have just been turned on?

### The lamp is cold so low resistance, high current flows - sometimes enough to melt the wire in the bulb

34

## In a potential divider, what happens to voltage when two resistors are equal?

### They share applied voltage equally

35

## In a potential divider, a current passes through a resistor then through a thermistor. How does the voltage across each component change as temperature decreases?

### The thermistor cools. The resistance of the thermistor rises, taking a larger share of input voltage. As the input from the battery is constant so output voltage rises across the fixed resistor.

36

## In a potential divider, a current passes through a resistor then through a thermistor. How does the voltage across each component change as temperature increases?

### The thermistor heats up. The resistance of the thermistor decreases, taking a smaller share of input voltage. As the input from the battery is constant so output voltage decreases across the fixed resistor.

37

## In a potential divider, a current passes through a resistor then through an LDR. How does the voltage across each component change as light intensity increases?

### If light intensity increases the resistance of the LDR decreases. The LDR will take a smaller share of the input voltage. As the input voltage from the battery is fixed the output voltage across the fixed resistor must increase.

38