You are Here: Home >< Physics

# Resistance Exam Question! Watch

1. A cell is in series with two boxes, P and Q.

• Each box contains two resistors in parallel.
• One of the four resistors has a value of 1 Ohm.
• Each of the other resistors has a value much greater than 1 Ohm

a) State what measurements the student, with the aid of a voltmeter, must take in order to determine which box contains the 1.0 Ohm resistor.

b)Explain how the measurements you describe would enable the student to make the correct identification of the box with the 1 Ohm resistor.

OUCH!
2. (Original post by Scapepicture)
A cell is in series with two boxes, P and Q.

• Each box contains two resistors in parallel.
• One of the four resistors has a value of 1 Ohm.
• Each of the other resistors has a value much greater than 1 Ohm

a) State what measurements the student, with the aid of a voltmeter, must take in order to determine which box contains the 1.0 Ohm resistor.

b)Explain how the measurements you describe would enable the student to make the correct identification of the box with the 1 Ohm resistor.

OUCH!
Well, for (a);
You would obviously need to have an ammeter connected in series as well.
You would need to take measurements of varying potential difference and the current corresponding to each p.d, because that is what you need to calculate the resistance using R=V/I

for (b);
Most questions like this would want you to plot a graph, so plot a graph of current against p.d, and then find the gradient which would probably be a straight line assuming the practical was done properly.

The gradient of the graph would represent the resistance;
and presumably you would know the formula for resistors in parallel would be;
R= 1/R1 + 1/R2 and etc.
As you know one of the resistors is a 1 ohm resistor, the formula would change into,

R= 1 + 1/R2

And you could probably find the box which contains the 1 ohm resistor using this method.

Hope I helped
3. (Original post by Scapepicture)
A cell is in series with two boxes, P and Q.

• Each box contains two resistors in parallel.
• One of the four resistors has a value of 1 Ohm.
• Each of the other resistors has a value much greater than 1 Ohm

a) State what measurements the student, with the aid of a voltmeter, must take in order to determine which box contains the 1.0 Ohm resistor.

b)Explain how the measurements you describe would enable the student to make the correct identification of the box with the 1 Ohm resistor.

OUCH!
The box with the 1 ohm and the large resistor in will have a total resistance of very nearly one ohm.
The other box will have a resistance which is much higher.
For example, if it was two 100 ohm resistors it would be 50 ohms.
You just need to find out which box has the higher resistance. V=IR should do the trick.

TSR Support Team

We have a brilliant team of more than 60 Support Team members looking after discussions on The Student Room, helping to make it a fun, safe and useful place to hang out.

This forum is supported by:
Updated: December 20, 2010
Today on TSR

### Degrees to get rich!

... and the ones that won't

### Women equal with Men?

Discussions on TSR

• Latest
• ## See more of what you like on The Student Room

You can personalise what you see on TSR. Tell us a little about yourself to get started.

• Poll
Discussions on TSR

• Latest
• ## See more of what you like on The Student Room

You can personalise what you see on TSR. Tell us a little about yourself to get started.

• The Student Room, Get Revising and Marked by Teachers are trading names of The Student Room Group Ltd.

Register Number: 04666380 (England and Wales), VAT No. 806 8067 22 Registered Office: International House, Queens Road, Brighton, BN1 3XE

Reputation gems: You get these gems as you gain rep from other members for making good contributions and giving helpful advice.