Analyze the following statements about a circuit containing three resistors with different resistances, associated in parallel and submitted to a different potential.

Question

Verify if the statements are true or false.

1 - The resistance of the equivalent resistor is smaller than the smallest of resistances of these resistors.

2 - A electrical current is smaller in the biggest resistance' resistor

3 - The electrical dissipated potential is bigger at the most resistant resistor.

A) False, True, False

B) True, False, False

C) True, True, True

D) True, True, False

E) False, False, True

Answer 1

Hi Joey E.,

If you've been paying attention in your course, you should know by now that 1/R = 1/R₁ + 1/R₂ + ... for resistors in parallel. So put in numbers for resistors of ohmage 2,3, and 6 and see what you come up with for R (total) . That should clue you into part 1.

Now, since the voltage across all three resistors is identical, what do you think is true about statement 2? Remember that resistance means, the resistor doesn't want to pass current!

For item 3, I have no idea what dissipated potential is, other than (perhaps) a student who doesn't do the work he/she is capable of! If it means power dissipated (as heat), then you should start shuttling your basic equations around: Power(or work) = I*V and I = V/R . Important note: You can always create these equations yourself by re-thinking: If I pass more current I can do more work, and if I use higher voltage current I can do more work. Current and voltage combined do work! And: If I boost voltage I'll get more current passed, and if I increase resistance I'll get less current passed.

OK then, Power = (V/R)*V = V^2 / R . That should clue you in on item 3.

Hopefully you passed right on over the part of the question that said "and submitted to a different potential"; if you wire the resistors in parallel then they are submitted to the same potential (=voltage), period!

If this question came from a teacher, shame! If from a "review guide", take it as a warning that not all brands of review guide are equally well proof-read or even error-free on their answers. Just sayin'.

-- Cheers, --Mr. d.