Resistance relation with temp [THERMISTORS] help

Watch
KINGYusuf
Badges: 12
Rep:
?
#1
Report Thread starter 6 years ago
#1
Q: 'Explain what will happen to the reading on the voltmeter as the temperature of the greenhouse increases"



So I know that for thermistors the lower the temperature, the greater the resistance.

Since V=IR, shouldn't a greater R mean a greater V?

The mark scheme says that the voltmeter reading decreases




The circuit diagram is basically an input V of 6V with a variable resistor and a 1000ohm resistor in series. But the resistor parallel with a voltmeter (if anyone's wondering)
0
reply
TARS
Badges: 3
Rep:
?
#2
Report 6 years ago
#2
The temperature of the greenhouse increases

The temperature of the thermistor subsequently increases

The resistance of the thermistor decreases due to the increase in temperature

The effective resistance of the thermistor and parallel resistor increases (given by Σ(r1 +r2)-1)

The potential difference therefore increases in the thermistor and parallel resistor part

The potential difference therefore decreases for the other resistor


---------------------------

You understand that the resistance of the thermistor and the resistor in parallel to it is due to the sum of the negative reciprocals of the resistances? So if the resistance of the thermistor decreases, the effective resistance is greater due to the law of parallel resistances.

If Rt is the resistance of the thermistor, and Rn is the resistance of the resistor in parallel:

Image

If the resistance of the thermistor decreases, you must be able to see that the effective resistance will increase.

Image
0
reply
X

Quick Reply

Attached files
Write a reply...
Reply
new posts
Back
to top
Latest
My Feed

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.

Personalise

Have you made your mind up on your five uni choices?

Yes, and I've sent off my application! (151)
54.91%
I've made my choices but havent sent my application yet (38)
13.82%
I've got a good idea about the choices I want to make (31)
11.27%
I'm researching but still not sure which universities I want to apply to (26)
9.45%
I haven't started researching yet (16)
5.82%
Something else (let us know in the thread!) (13)
4.73%

Watched Threads

View All