Ohm's law V=I×R???

Rose2000

Hi. I was just wondering about the used resistor in ohm's law circuit. In our textbook it uses a heating coil in a beaker of water. My question is if the temperature of the heating coil changes (increases) does the resistance not change? therefore the resistance is not constant ohm's law shouldn't apply? It's probably an easy answer question but I'd greatly appreciate if anyone could help. Thanks

Icemancometh

Rose2000 wrote: »

Hi. I was just wondering about the used resistor in ohm's law circuit. In our textbook it uses a heating coil in a beaker of water. My question is if the temperature of the heating coil changes (increases) does the resistance not change? therefore the resistance is not constant ohm's law shouldn't apply? It's probably an easy answer question but I'd greatly appreciate if anyone could help. Thanks

Not a physicist, but I'll give my uneducated reply. The resistance changes (increases with heat), but Ohm's law still applies, just with a different resistance. A comparison would be with a moving car. Air resistance increases with velocity (velocity squared I think). So a car might be accelerating according to the formula F=ma, but as velocity increases, a reduces due to air resistance (assuming constant thrust).

There are some clips on YouTube of people cooling conductors to demonstrate the change in amperage due to the reduced resistance. Pretty cool demonstration of the principle.

Cooling increases current increases power of electromagnet.

Sh1tbag OToole

It will increase but only a small bit. I suppose the beaker is a bad example because the temperature doesnt stay constant. If it was a heating element inside in a pipe with water flowing past it the whole time it will stay constant

gctest50

Rose2000 wrote: »

Hi. I was just wondering about the used resistor in ohm's law circuit. In our textbook it uses a heating coil in a beaker of water. My question is if the temperature of the heating coil changes (increases) does the resistance not change? therefore the resistance is not constant ohm's law shouldn't apply? It's probably an easy answer question but I'd greatly appreciate if anyone could help. Thanks

kinda

temp resistance
############################### Ag #################################

1 0.000752445447705
4 0.000752445447705
7 0.000775018811136
10 0.000865312264861
15 0.001422121896163
20 0.003175319789315
25 0.007185854025583
30 0.014597441685478
35 0.025658389766742
40 0.040556809631302
45 0.0581640331076
50 0.078254326561324
55 0.099322799097065
60 0.121896162528217
70 0.169300225733634
80 0.217456734386757
90 0.266365688487585
100 0.314522197140707
125 0.431151241534989
150 0.54627539503386
175 0.660647103085026
200 0.774266365688488
225 0.887133182844244
250 1
300 1.225733634311512

############################### Au #################################

1 0.011802575107296
4 0.011802575107296
7 0.011856223175966
10 0.012124463519313
15 0.013841201716738
20 0.018562231759657
25 0.026931330472103
30 0.038894849785408
35 0.054613733905579
40 0.075643776824034
45 0.097103004291845
50 0.118562231759657
55 0.144849785407725
60 0.165236051502146
70 0.211909871244635
80 0.258047210300429
90 0.303648068669528
100 0.348712446351931
125 0.459763948497854
150 0.569206008583691
175 0.677038626609442
200 0.784334763948498
225 0.891630901287554
250 1
300 1.218347639484979

############################### Cu #################################

1 0.001441961067051
4 0.001441961067051
7 0.001441961067051
10 0.001456380677722
15 0.001571737563086
20 0.002018745493872
25 0.00323720259553
30 0.005969718817592
35 0.010598413842826
40 0.017231434751262
45 0.025811103100216
50 0.037346791636626
55 0.052415284787311
60 0.070007209805335
70 0.111031002162942
80 0.155010814708003
90 0.202595529920692
100 0.250901225666907
125 0.37635183850036
150 0.503965392934391
175 0.63013698630137
200 0.754145638067772
225 0.877433309300649
250 1
300 1.243691420331651

############################### Hf #################################

1 0.036549707602339
4 0.036549707602339
7 0.036549707602339
10 0.036622807017544
15 0.037171052631579
20 0.040570175438596
25 0.047733918128655
30 0.059868421052632
35 0.075438596491228
40 0.092214912280702
45 0.109356725146199
50 0.127266081871345
60 0.165423976608187
70 0.205409356725146
80 0.246747076023392
90 0.289583333333333
100 0.333260233918129
150 0.548611111111111
200 0.76827485380117
250 1

############################### Mn #################################

0 0.048484848484848
1 0.049330514446794
4 0.061945031712474
7 0.089781536293164
10 0.13276955602537
15 0.238195912614517
20 0.377730796335448
25 0.53276955602537
30 0.658210007047216
40 0.814658210007047
50 0.888653981677237
60 0.92107117688513
70 0.933756166314306
80 0.930232558139535
90 0.926708949964764
100 0.930937279774489
150 0.957716701902748
200 0.980267794221282
250 1
300 1.016208597603946

############################### Mo #################################

1 0.000163475011677
4 0.000168145726296
7 0.000182157870154
10 0.000205511443251
15 0.000310602522186
20 0.000602522185894
25 0.001307800093414
30 0.002802428771602
35 0.005791686127978
40 0.010649229332088
50 0.025852405418029
60 0.048108360579169
70 0.077066791219057
80 0.112330686595049
90 0.153666510976179
100 0.200373657169547
150 0.464502568893041
200 0.73120037365717
250 1

############################### Pd #################################

1 0.002252252252252
4 0.002308558558559
7 0.002443693693694
10 0.002725225225225
15 0.003896396396396
20 0.00634009009009
25 0.010540540540541
30 0.016891891891892
35 0.025900900900901
40 0.037612612612613
45 0.051801801801802
50 0.068243243243243
55 0.086148648648649
60 0.105630630630631
70 0.148648648648649
80 0.197072072072072
90 0.246621621621622
100 0.295045045045045
125 0.420045045045045
150 0.540540540540541
175 0.658783783783784
200 0.774774774774775
225 0.888513513513514
250 1
300 1.216216216216216

############################### W #################################

0 0.000003488372093
1 0.000003651162791
4 0.000006209302326
7 0.000013488372093
10 0.000031860465116
15 0.000131860465116
20 0.000455813953488
25 0.001286046511628
30 0.003093023255814
40 0.012627906976744
50 0.032790697674419
60 0.061860465116279
70 0.098139534883721
80 0.14093023255814
90 0.188139534883721
100 0.237209302325581
150 0.485581395348837
200 0.73953488372093
250 1

############################### Zn #################################

1 0.000012187690433
4 0.000014686166971
7 0.000052813325208
10 0.000253910217347
15 0.001850497664026
20 0.006967296364006
25 0.015722120658135
30 0.027422303473492
40 0.057891529555149
50 0.094454600853138
60 0.134470851107049
70 0.175705870404225
80 0.217753402396912
90 0.260207190737355
100 0.303676619947187
150 0.527320739386553
200 0.760105626650416
250 1

############################### Zr #################################

1 0.007163323782235
4 0.007163323782235
7 0.007249283667622
10 0.007249283667622
15 0.00810888252149
20 0.010229226361032
25 0.014040114613181
30 0.020372492836676
40 0.041289398280802
50 0.071404011461318
60 0.107449856733524
70 0.147277936962751
80 0.189971346704871
90 0.234097421203438
100 0.280229226361032
150 0.511174785100287
200 0.754441260744986
250 1

more later

papu

This may help

http://www.explainthatstuff.com/resistors.html

The resistance of a resistor isn't constant, even if it's a certain material of a fixed length and area: it steadily increases as the temperature increases. Why? The hotter a material, the more its atoms or ions jiggle about and the harder it is for electrons to wriggle through, which translates into higher electrical resistance. Broadly speaking, the resistivity of most materials increases linearly with temperature (so if you increase the temperature by 10 degrees, the resistivity increases by a certain amount, and if you increase it by another 10 degrees, the resistivity rises by the same amount again)

Ohms law still applies ontop of this.