6. what is an i-v characterisitc curve? lesson · 9/6/2019 · what is an i-v characteristic...

CW Nov 26, 2018

What is an I-V characteristic curve?

Describe how resistance would change in a wire if the temperature were raised.

Complete the sentence. Current is measured by an _______ in series. Potential difference is measured by a voltmeter in ________.

Explain how you could calculate the resistance of a wire in series with a power pack.

Current is measured by an ammeter in series. Potential difference is measured by a voltmeter in parallel.

Describe how resistance would change in a wire if the temperature were raised. The greater the temperature, the greater the resistance.

Explain how you could calculate the resistance of a wire in series with a power pack. Measure the current, using an ammeter and the p.d. across the wire. Resistance is then calculated by dividing the p.d. by the current.

Learning objectives

Sketch and explain the current-voltage characteristic of an ohmic resistor and a filament lamp.

State Ohm’s Law

Describe how the voltmeter and ammeter are connected

Explain why the meters are connected in this way

State Ohm’s Law. V = IR.

Describe how the voltmeter and ammeter are connected. Voltmeter in parallel and the ammeter in series.

Explain why the meters are connected in this way. The current is the rate of flow of charge so it is effectively counting charges flowing though it. The voltmeter measures the difference in energy per unit charge either side of a component.

Conclusion:*

What*are*the*variables?*

Dependent*variable:*

Hypothesis**

If*I*increase/decrease*_________,*then*the*__________*will*increase/

decrease/stay*the*same*

Graph*predicAon*

Equipment:*• ________________________*• ________________________*• ________________________*• ________________________*• ________________________*

Method:*1.  ______________________*2.  ______________________*3.  ______________________*4.  ______________________*5.  ______________________*

Risk*assessment* EvaluaAon*

Experiment:*

Independent*variable:*

Table*of*results*

______*/___* ______*/___*** **** **** **** **** **

ExplanaAon:*

This is what you could change. You can only

change one.

This is what you change

This is what you measure

This is a prediction.

What do you need to

investigate?

How will you carry out

your investigation.

What are the dangers?

What could you do better?

What did you find out?

Why did this happen?

How do the shape of IV characteristic curves vary for different components?

Component, p.d., current, resistance, resistivity, temperature, light,

Potential difference / V

Current / A

p.d.

currentXXXX

XXXXXXXXXXp.d / V.

Cur

rent

/ A

p.d. / V Current / A

Various componentsPowerpackKettle / lampConnecting wires

Measure the p.d. across the component.

Repeat within the range of -6V to +6V.

Connect a component in series.

Plot an I-V graph.

Do not leave the current on for long as this could cause heating. Switch off

current between measurements. Avoid liquids near to the electrical equipment.

XXXXXXXXXX

Measure the current.

Multimeter x 2

Complete 5 data points for both components



Voltage across component / V Current through resistor / mA Current through filament lamp / mA

Voltage across component / V Current through resistor / mA Current through filament lamp / mA

0.3 0.0 5.4

1.3 0.5 14.9

2.3 1.0 22.2

3.3 1.4 28.3

4.3 1.9 33.7

5.3 2.4 38.6

6.4 2.9 43.0

7.4 3.3 47.5

8.5 3.8 51.1

9.6 4.3 54.8

-0.3 -0.0 -5.4

-1.3 -0.5 -14.9

-2.3 -1.0 -22.2

-3.3 -1.4 -28.3

-4.3 -1.9 -33.7

-5.3 -2.4 -38.6

-6.4 -2.9 -43.0

-7.4 -3.3 -47.5

-8.5 -3.8 -51.1

-9.6 -4.3 -54.8

Plot both sets of data on the prepared graph

Add lines of best fit for the two data sets

Explain the shapes of the data patterns

An IV characteristic curve for a resistor and a filament lampC

urre

nt /

mA

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0

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Voltage / V

-10 -9 -8 -7 -6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6 7 8 9 10

Plot both sets of data on the prepared graph

Add lines of best fit for the two data sets

Explain the shapes of the data patterns

Add lines of best fit

State whether the components follow Ohm’s Law or not

Give your reasons


urre

nt /

mA

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Voltage / V

-10 -9 -8 -7 -6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6 7 8 9 10

Add lines of best fit

State whether the components follow Ohm’s Law or not

Give your reasons


urre

nt /

mA

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Voltage / V

-10 -9 -8 -7 -6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6 7 8 9 10

Lamp is non-Ohmic, It does not follow Ohm’s Law (R =V/I). The gradient is not

constant.

Resistor is Ohmic, it follows Ohm’s Law

(R = V/I). The gradient is constant, equal to 1/R.


urre

nt /

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-5

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-3

-2

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0

1

2

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5

Voltage / V

-10 -9 -8 -7 -6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6 7 8 9 10


urre

nt /

mA

-5

-4

-3

-2

-1

0

1

2

3

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Voltage / V

-10 -9 -8 -7 -6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6 7 8 9 10

I = 1/R V 1/R = I/V

1/R = (8 mA / 18 V) 1/R = (8/1000)A / 18 V 1/R = 0.008A / 18 V 1/R = 0.00044 Ω-1

R = 2250 Ω8 mA

18 V


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Voltage / V

-10 -9 -8 -7 -6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6 7 8 9 10

State how you know that the lamp is non-Ohmic

Describe the shape of the graph at 3 or more points

Explain why the graph has the shape it has


urre

nt /

mA

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Voltage / V

-10 -9 -8 -7 -6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6 7 8 9 10

1/R is not constant so R is not

constant. How does R change with V?

1/R is large so R is small

1/R is smaller, so R

is larger

1/R is getting smaller, so R is

even larger

As V increases, I increases. The electrons hit the metal

ions harder and faster transferring their electrical energy to heat: the metal ions vibrate faster. They block the electrons so

reducing the current: this means the resistance is

increasing.

Learning objectives

Sketch and explain the current-voltage characteristic of an ohmic resistor and a filament lamp.

What is an I-V characteristic curve?

Answer this in as much detail, and as fully as you can. This will determine whether or not you have achieved the learning objective and the level to

which you have achieved it.

Think about what you have learned and how it relates to what you already

know.

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A

X

V

Gradient changes

Lamp heats upGreater chance of electron collisionsResistance increases

Old stuffPhysics only

Choose a component and complete the prepared table.

Choose two components and complete the prepared table.

Obtain data on multiple components.

Poten&al)difference)/)V) Current)/)A)46.11) 40.22)45.27) 40.20)44.41) 40.18)43.57) 40.16)42.49) 40.13)41.65) 40.11)40.84) 40.07)40.15) 40.04)0.15) 0.04)0.86) 0.08)1.67) 0.11)2.48) 0.14)3.59) 0.17)4.44) 0.19)5.27) 0.21)6.13) 0.22)

Poten&al)difference)/)V) Current)/)A)44.95) 0.00)44.03) 0.00)42.90) 0.00)42.06) 0.00)41.24) 0.00)40.46) 0.00)0.46) 0.00)1.18) 0.00)1.89) 0.02)2.66) 0.06)3.74) 0.09)4.62) 0.12)


Resistance wire

LEDFilament lamp

Plot your data on the graph. Add a line of best fit. Is it linear?

Construct a graph of your data. Add a line of best fit. Is it linear?

Construct more than one graph of your data.




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Poten,al'difference'/'V'

A'graph'to'show'the'I:V'characteris,cs'of'a'filament'lamp.'

0"

0.02"

0.04"

0.06"

0.08"

0.1"

0.12"

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A'graph'to'show'the'I:V'characteris,c'of'30'cm'of'32'SWG'nichrome'wire.'

State the relationship between the two variables.

Construct a graph of your data. Add a line of best fit. Is it linear?

Construct more than one graph of your data.




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urre

nt /

mA

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Voltage / V

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Voltage across component / V

Current through resistor / mA

Current through filament lamp / mA

6. what is an i-v characterisitc curve? lesson · 9/6/2019 · what is an i-v characteristic...

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