Question

A 120-V hair dryer has two settings: 850 W and 1250 W.

A) at which setting do you expect the resistance to be higher?After making a guess,determine the resistance at

B)the lower setting;and

C) the higher setting

Please show work.

Answer 1

A) P=V^2 /R, so assuming that the voltage is the same for bothhairdryers, the one with higher power should have a lowerresistance (they are inversely proportional)

B) P=V^2 /R   --> R= 120^2 /850W = 16.94 Ω

C) P=V^2 /R   --> R= 120^2 / 1250W = 11.52 Ω

Answer 2

A 120-V hair dryer has two settings: 850 W and 1250 W.

A) at which setting do you expect the resistance to be higher?After making a guess,determine the resistance at

B)the lower setting;and

C) the higher setting

Please show work.
power=voltage*current
but voltage =current*resistance
so current=V/R
hence power=(voltage)²/resistance
which clearly indicates
that power is inversely proportional to resistance
hence resistance is higher for 850W
B)
R=V*V/P=120*120/850=16.9411ohm
C)
R=V*V/P=120*120/1250=11.52ohm

Answer 3

The hair dryer has 2 settings R 850 W R 1250 W The relation between the voltage and the power, resistance is given as: T2

The power is inversely related to the resistance. The greater the resistance, the lesser is the power Hence, the setting with lower power has greater resistance. Therefore, the setting with 850 watts has greater resistance. The resistance for the lower power setting is: Rearrange for the resistance and calculate the resistance as follows: V2 (120v) 850 W :: 16.94 Ω The resistance is 16.94 Ω. The resistance for the higher power setting is: V2 (120 v) 1250 W 11.52 Ω The resistance is 1 1.5262.