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Physics Section 3: Current Electricity > I/V Characteristics > Flashcards

Flashcards in I/V Characteristics Deck (23)
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0

The shallower the gradient of a characteristic I/V graph, the .... The resistance of the component

Greater

1

What does the I/V characteristic graph for a metallic conductor look like

Exactly the same as one for a ohmic conductor

2

What does the I/V characteristic graph for a filament lamp look like

Curve
Starts STEEP gets SHALLOWER as voltage rises

3

What does a filament lamp not have the same characteristic graph as a metallic conductor as the lamp is a coiled-up length of metal wire

Because the CURRENT flowing through the lamp increases it's TEMPERATURE
The RESISTANCE of a metal increases as the TEMPERATURE increases

4

What are semi conductors used in

Sensors

5

Why are semiconductors nowhere near as good at conducting electricity as metals

They have fewer CHARGED CARRIERS available

6

What makes semiconductors excellent sensors for changes in the environment

If ENERGY is SUPPLIED to the semiconductor
More CHARGE CARRIERS can be released

7

Name three semiconductors

Thermistors
LDRs
Diodes

8

What is a thermistor

A RESISTOR that depends on TEMPERATURE

9

What does the NTC thermistor stand for

Negative Temperature Coefficient

10

What does negative temperature coefficient mean

The RESISTANCE decreases as the TEMPERATURE goes up

11

What does the characteristic graph for a thermistor show

Curves upwards
Starts shallower gets sleeper

12

Explain in terms of temperature and current why the resistance decreases

Increasing the CURRENT through a thermistor increases it's TEMPERATURE
The increasing GRADIENT of this characteristic graph tells you that the RESISTANCE is decreasing

13

Explain why warming the thermistor makes the resistance lower

Gives more ELECTRONS enough ENERGY to ESCAPE from their atoms
This means more CHARGE CARRIERS available

14

What does the resistance of an LDR depend on

Light intensity

15

What does LDR stand for

Light-dependent resistor

16

The greater the intensity of light shining on the LDR, the .... The resistance

Lower

17

Why does the more light shining on a thermistor lower the resistance

Light provides ENERGY for the ELECTRONS to ESCAPE from their atom
More CARGE CARRIERS mean lower resistance

18

Diodes only let what

Current flow in one direction

19

Give an example of a diode

LED (light-emitting diode)

20

Symbol for: thermistor
LDR
Diode

Rectangle horizontal diagonal
Circle two lines in top left
Circle triangle verticle

21

What 3 things do diodes do

1) FORWARD bias us the DIRECTION in which the CURRENT is allowed to flow
2) most diodes require a THRESHOLD VOLTAGE of about 0.6V in the FORWARD direction before they will conduct
3) in REVERSE bias, the RESISTANCE of the diode is very HIGH and the CURRENT that flows is very TINY

22

How do you work out energy wasted

Current square
* resistance
* time