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EVIL ocr physics planning exercise

okay, here's the deal:

i'm a pretty decent as physics student - i got 90/90 in the module 1 :tongue:

but this planning exercise has had me tearing my hair out

my teacher says "theres plenty of information on strain gauges on the internet"

but thats a load of crap

i can find nothing of any use

i've clocked up about 18 hours on the internet researching

but nothing

so i need some help

and i DON'T wanna hear nothing about no "wheatstone bridge"

i don't know what material to use as a test subject, or the range of forces to be applied

so please,

save my sanity

thank you :biggrin:

Reply 1

t-t-t-tommo

OP

c'mon, man

i got my formal write-up tomorrow :eek:

Reply 2

SunGod

Everyone gets a different assignment for this coursework,tell us what you exactly have to do.

Reply 3

LS.

8

This thread might help: Physics OCR planning exercise

I have to admit, I usually find this type of coursework easy, but this physics one isn't exactly straightforward.

ignore this.

OP

alrighty...

You are required to design a laboratory experiment to investigate how the electrical resistance of a strain gauge attached to a flat surface depends on the tensile force applied to the surface

You should draw a diagram of the arrangement of your apparatus, and in your account you should pay particular attention to

(a) the procedure to be followed

(b) the material on which the strain gauge is to be mounted and the dimensions of this material

(c) the method of attaching the strain gauge to the material

(d) how the force would be applied

(e) the approximate range of forces you would use

(f) how the resistance of the strain gauge would be measured, including the ranges of any meters used

(g) any safety precautions you would take when carrying out the investigation

(h) particular features of the design that would ensure the accuracy and reliability of you results

any help at all would be valued and appreciated

Reply 6

t-t-t-tommo

OP

here's what i got so far:

:confused:

the test specimen is "stiff rubber"
:confused:

the strain gauge will be attached to it by "epoxy adhesive"
:confused:

the stiff rubber will be clamped to a table
:confused:

an increasing load will be hung from the stiff rubber at the edge of the table
:confused:

the resistance will be measured by means of a basic circuit with a voltmeter in parallel and ammeter in series with the strain gauge

Reply 7

igloo

1

t-t-t-tommo

here's what i got so far:

:confused:

the test specimen is "stiff rubber"
:confused:

the strain gauge will be attached to it by "epoxy adhesive"
:confused:

the stiff rubber will be clamped to a table
:confused:

an increasing load will be hung from the stiff rubber at the edge of the table
:confused:

the resistance will be measured by means of a basic circuit with a voltmeter in parallel and ammeter in series with the strain gauge

Stiff rubber? doesn't your test specimen have to be able to conduct electricity in order to be able to measure its resistance- feel free to correct me if i'm wrong here.
i was thinking of using aluminium wire- because it has a low youngs modulus- is this right?
you can use a G-clamp to clamp the specimen to the table.
how would you attach the weight to the specimen- construct some kind of hook and add a strip of sellotape perhaps?

Reply 8

lostandconfused

t-t-t-tommo

here's what i got so far:

:confused:

the test specimen is "stiff rubber"
:confused:

the strain gauge will be attached to it by "epoxy adhesive"
:confused:

the stiff rubber will be clamped to a table
:confused:

an increasing load will be hung from the stiff rubber at the edge of the table
:confused:

the resistance will be measured by means of a basic circuit with a voltmeter in parallel and ammeter in series with the strain gauge

why stiff rubber and epoxy adhesive?
where did u get this info from?

please help!

Reply 9

LS.

8

lostandconfused

why stiff rubber and epoxy adhesive?
where did u get this info from?

please help!

If you look up information on strain gauges, you'll find out why this adhesive was used.

As for the rubber, I'm not using that in my plan.

Reply 10

lostandconfused

LS.

If you look up information on strain gauges, you'll find out why this adhesive was used.

As for the rubber, I'm not using that in my plan.

what are u using?

Reply 11

FaerieLand

When's your deadline?? mine was last thurs, managed to finish it ok, it just seems difficult at first, but i had to have a lot of explainig done, so hopefully i can pass on some knowledge, fire away!

Reply 12

lostandconfused

FaerieLand

When's your deadline?? mine was last thurs, managed to finish it ok, it just seems difficult at first, but i had to have a lot of explainig done, so hopefully i can pass on some knowledge, fire away!

yay! thanku! its due on wednesday. i dont know what material to attach the strain gauge to and what adhesive to use, and why
please help!

Reply 13

FaerieLand

lostandconfused

yay! thanku! its due on wednesday. i dont know what material to attach the strain gauge to and what adhesive to use, and why
please help!

ok, first of all, we attached the strain gague to a plastic, reasonably thin as this will let it stretch in laboratory conditions, metal would have been ideal but would need too strong force. As you're using plastic, either a really strong plastic glue would work or an epoxy resin such as araldite. If you type epoxy resin into google, it will give you safety risks, and why you should use it

circuit; think about using either multimeter if you use these at school or the standard circuit, voltmeter &ammeter

anything else?

Reply 14

lostandconfused

FaerieLand

ok, first of all, we attached the strain gague to a plastic, reasonably thin as this will let it stretch in laboratory conditions, metal would have been ideal but would need too strong force. As you're using plastic, either a really strong plastic glue would work or an epoxy resin such as araldite. If you type epoxy resin into google, it will give you safety risks, and why you should use it

circuit; think about using either multimeter if you use these at school or the standard circuit, voltmeter &ammeter

anything else?

could u use Perspex? like as in attach the strain gauge to a Perspex ruler, i was thinking..
im going to use a voltmeter and ammeter.
do u kno how big strain gauges are? i need to write dimensions in the plan as well.

thank u so much!

Reply 15

lostandconfused

also the adhesive i keep coming across is cyanocrylate (super-glue), not epoxy adhesive

Reply 16

FaerieLand

lostandconfused

could u use Perspex? like as in attach the strain gauge to a Perspex ruler, i was thinking..
im going to use a voltmeter and ammeter.
do u kno how big strain gauges are? i need to write dimensions in the plan as well.

thank u so much!

i just put "thin plastic", so not sure, umm think they vary, i think you just have to put the dimensions of the plastic you will mount it on, so it can be whatever you like; eg 15cm x 8cm or something like that.

Reply 17

FaerieLand

lostandconfused

also the adhesive i keep coming across is cyanocrylate (super-glue), not epoxy adhesive

super glue isn't supposed to be strong enough, epoxy resin is a two part and much stronger industrial glue. Try looking up the "properties of adhesives", see what that gives you

Reply 18

lostandconfused

thank u sooooo much! i could kiss u!
seriously thank u, finally know what to use! :smile:

Reply 19

FaerieLand

lostandconfused

thank u sooooo much! i could kiss u!
seriously thank u, finally know what to use! :smile:

lol! its ok, the amount of people i bugged to help me with mine thought it was the least i could do to help other ppl, hope it goes ok, i guess you probably also have the pratical exam on weds? thats the bit im dreading!

EVIL ocr physics planning exercise

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