Stuck with physics, help? lol?

Question

A strain gauge is a device that detects force. It is made from a thin piece of wire set into a flexible piece of plastic. When the plastic bends the wire stretches this causes the electrical resistance of the gauge to change.

any help/advice please

before being stretched, a gauge correctly connected to a 3V battery has a current of 0.025A flowing through it.

i) calculate the resistance of the unstretched gauge.

ii) when the gauge is stretched, the current flowing through it changes to 0.022A. State how the resistance of the gauge has changed .

Answer 1

1)i) Voltage = Current * Resistance

So, Resistance = Voltage / Current

Resist. = 3 / 0.025 = 120 Ohms

ii) 3 / 0.022 = 136.36 Ohms

The resistance has increased as the strian gauge will have been lengthened (and its cross sectional area reduced) slightly causing the increase in resistance; from this information we could then calculate how much strain the gauge has undertaken to work out an exact increases in length of the sample we are testing.

Answer 2

Both parts are solved with Ohm's Law: V = I R

where V = voltage, R = resistance, and I = current.

(a) 3 V = ( .025 A ) R

R = 120 Ohms

(b) 3 V = ( .022 A ) R

R = 137 Ohms

Answer 3

I) V (voltage) = I (current) *R (resistance)

==>V=IR

==>V/I=R

==>3/0.025=120R

II)The resistance has increased slightly.

This is why ==>

Re-arranging the above equation we get,

==>V/R=I

If I has decreased, and V is the same, R must have increased so the division gives a slightly smaller value.

Answer 4

V = Voltage

I = Current

R = Resistance

i) V = IR

3 = 0.025  x R

R = 3/0.025

R = 120 Ohms

ii) V = IR

3 = 0.022 x R

R = 3/0.022

R = 136.36 Ohms (to 2 dp)

The resistance has increased.

EDIT: The answer in the first post of 137 Ohms is INCORRECT and the reason given for the increase in the second post is also INCORRECT - all they want you to do is to notice that there has been an increase, not to guess at why (advanced Chemistry).