a falkirk high school presentation ohm’s law for each of the questions, click the letter of the...

A Falkirk High School presentation

Ohm’s Law

For each of the questions, click the letter of the correct answer Click to Click to

start the start the testtest

When a resistor is connected to a 3 Volt battery, a current of 6 Amps flows through it. Calculate the size of the resistor.

B

C

D

A 0.5 ohms

2 ohms

3 ohms

18 ohms

1 a

V

A


First draw the triangle that links voltage, current and resistance

the answer

R I

V

Sorry you’re wrong, let me show you how to do it.

the question

Now write down what the question is asking you to calculate. (Resistance)

R =

Now cover up R with your finger

And see what’s left in the triangle

I

V6

3= = 0.5 ohm

Now substitute the numbers into the equation and calculate the answer.

Click here for the next question

V

I


A

B

C

D

98 ohms

4 ohms

1.5 ohms

0.66 ohms

1 b

When a resistor is connected to a 240 Volt supply, a current of 6 Amps flows through it. Calculate the size of the resistor.

A

B

C

D

40 ohms

20 ohms

10 ohms

0.025 ohms

1 c

When a resistor is connected to a 9 Volt battery, a current of 45 milliamps flows through it. Calculate the size of the resistor.

A

B

C

D

6 ohms

0.2 ohms

20 ohms

200 ohms

2 a

Before you can start a calculation, you must make sure all the measurements are in Standard Units.

R I

VThis is the same sort of calculation as before but this time the current is in milliamps.

To change milliamps to Amps, you must divide by 1000

So 45 milliamps = 45 / 1000 = 0.045 A

R =I

V0.045

9= = 200 ohms

so


When a resistor is connected to a 3 Volt battery, a current of 150 milliamps flows through it. Calculate the size of the resistor.

A

B

C

D

20 ohms

2 ohms

5 ohms

50 ohms

2 b

When a resistor is connected to a 1.5 Volt cell, a current of 150 milliamps flows through it. Calculate the size of the resistor.

A

B

C

D

0.1 ohms

100 ohms

1 ohms

10 ohms

2 c

Calculate the current that would flow through a 3 ohm resistor when it is connected to a 1.5 Volt cell.

A

B

C

D

2 A

4.5 A

0.5

1.5 A

3 a

Calculate the current that would flow through a 3 ohm resistor when it is connected to a 1.5 Volt cell.


the answer

R I

V


the question

Now write down what the question is asking you to calculate. (Current)

I =

Now cover up I with your finger


R

V3

1.5= = 0.5 A



V

R

Calculate the current that would flow through a 100 ohm resistor when it is connected to a 20 Volt supply.

A

B

C

D

0.1 A

0.2 A

5 A

2000 A

3 b

Calculate the current that would flow through a 30 ohm resistor when it is connected to a 3 Volt battery.

A

B

C

D

90 A

10 A

1 A

0.1 A

3 c

Calculate the current that would flow through a 3 k resistor when it is connected to a 6 Volt battery.

A

B

C

D

18 A

0.018 A

0.002 A

2 A

4 a

Before you can start a calculation, you must make sure all the measurements are in Standard Units.

R I

VThis is the same sort of calculation as before but this time the resistance is in k.

To change k to , you must multiply by 1000

So 3 k = 3 x 1000 = 3000

I =R

V3000

6= = 0.002 A

so



A

B

C

D

0.004 A

0.04 A

0.4 A

4 A

4 b


A

B

C

D

1 A

0.1 A

0.01 A

0.001 A

4 c

Calculate the voltage over a 6 resistor if a current of 12 A flows through it.

A

B

C

D

0.5 V

2 V

72 V

0.002 V

5 a



the answer

R I

V


the question

Now write down what the question is asking you to calculate. (Voltage)

V =

Now cover up V with your finger


R x I = = 72 V



6 x 12

R

I

Calculate the voltage over a 30 resistor if a current of 0.5 A flows through it.

A

B

C

D

60 V

15 V

0.0016 V

150 V

5 b


A

B

C

D

0.4 V

0.1 V

2.5 V

10 V

5 c

Calculate the current that would flow through a 60 resistor when it is connected to a 3 Volt battery.

A

B

C

D

0.05 mA

20 mA

50 mA

180 mA

6 a

Calculate your answer as before. R I

VThis is the same sort of calculation as before but this time the answer is in mA.

To change A to m, you must multiply by 1000

0.05 A = 0.05 x 1000 = 50 mA

I =R

V60 3= = 0.05 A

so


Calculate the current that would flow through a 480 resistor when it is connected to a 12 Volt battery.

A

B

C

D

25 mA

40 mA

0.025 mA

0.04 mA

6 b

Calculate the current that would flow through a 1000 resistor when it is connected to a 250 Volt supply.

A

B

C

D

2.5 mA

25 mA

250 mA

4 mA

6 c

When a resistor is connected to a 120 V supply, the current through it is measured to be 0.02 A. Calculate the size of the resistor.

A

B

C

D

6000 k

600 k

60 k

6 k

7 a

Calculate your answer as before. R I

VThis is the same sort of calculation as before but this time the answer is in k.

To change to k, you must divide by 1000

6000 = 6000 / 1000 = 6 k

R =I

V0.02

120= = 6000

so



A

B

C

D

0.1 k

1 k

10 k

100 k

7 b


A

B

C

D

2000 k

200 k

20 k

2 k

7 c

The picture shows a circuit used to determine the size of a resistor. Close-ups of the readings are shown.

Calculate the size of the resistor.

A

B

C

D

1.9

3.3

0.3

3.7

8 a

Sorry, you’re WRONG!

Maybe you’ve made a mistake in reading the meter scales.

The Voltmeter reading is 2.5 V

So the ammeter reading is 0.76 A

To calculate the resistance, you use

R =I V

0.76 2.5= = 3.3

On the ammeter, 0.7 would be here.7



A

B

C

D

1.9

9.4

2.4

1.2

8 b

Sorry, you’ve made another mistake.

Click here to go back and

try again



A

B

C

D

9.2

7.7

0.69

0.13

8 c


Click here to go back and try again

A

B

C

D

5

6

5000

0.2

9 aThe picture shows a circuit used to determine the size of a resistor. Close-ups of the readings are shown.


Sorry you’re wrong.

Maybe you didn’t notice that the ammeter was measuring in milliamps

To change mA to Amps, divide by 1000

So 0.3 mA = 0.3 / 1000 = 0.0003 A


A

B

C

D

4.1

4640

4800

4100

9 bThe picture shows a circuit used to determine the size of a resistor. Close-ups of the readings are shown.


A

B

C

D

8333

10000

10

8.3

9 cThe picture shows a circuit used to determine the size of a resistor. Close-ups of the readings are shown.


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a falkirk high school presentation ohm’s law for each of the questions, click the letter of the...

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