Determine the new current value

[Andre36]

Hi all.

Freshman electrical installations student here.

Please can someone help me with figuring out the formula to the following question, it's driving me nuts.

The current through the field windings of a motor is 1.8 amperes when the resistance is 100 ohms. After 5 minutes the resistance rises to 120 ohms. If the potential difference remains constant determine the new value of current flow. This is driving me nuts, because I have the answer but I cannot figure out the formula/how to get the answer.

Please can someone help me with what formula is, I have the answer but can't figure out how to reach it.

Thanks.

 

[telectrix]

V = IR ( ohms law)

as V is constant, then IxR must be constant

so: 1.8 x100 = 180V

so I = V/R = 180/120 = 1.5A

 

[i=p/u]

A b c ........to i and you telectrix, good example

 

[Des 56]

A motor is not the best example to use when trying to understand resistance
Where did this question arise?

 

[telectrix]

sounds like a college question, before progressing to inductance.

 

[Andre36]

V = IR ( ohms law)

as V is constant, then IxR must be constant

so: 1.8 x100 = 180V

so I = V/R = 180/120 = 1.5A

Thanks for this. Much appreciated.

 

[Andre36]

A motor is not the best example to use when trying to understand resistance
Where did this question arise?

College question paper. Can you suggest any other good websites? Ive learnt a bit from Youtube and such.