Physics Chapter 18 Ohm's Law

Which is the correct way to light the lightbuld with the battery

C would be correct, because the current can only flow if there is a continuous connection from the negative terminal through the bulb to the positive terminal.

You double the voltage across a certain conductor and you observe the current increases three time. What can you conclude?

A) Ohm’s Law is obeyed since the current still increases when V incrases

B) Ohm’s Law is not obeyed

C) This has nothing to do with Ohm’s Law

B) Ohm’s law is not obeyed, since the equation V= IR, states that the relationship between voltage and current is linear, so for a conductor that obeyed Ohm’s Law, the current must double when you double the voltage.

Two wires, AA andand BB, are made of the, are made of the
same metalsame metal and haveand have equal lengthequal length,,
but the resistance of wirebut the resistance of wire AA isis fourfour
timestimes the resistance of wirethe resistance of wire BB. How. How
do their diameters compare?do their diameters compare?

D_A = 1/2d_B. The resistance of wire A is greater because its area is less than wire B. Since area is related to radius (or diameter) squared, the diameter of A must be two times less than B

A wire of resistance RR isis
stretched uniformly (keeping itsstretched uniformly (keeping its
volume constant) until it is twicevolume constant) until it is twice
its original length. What happensits original length. What happens
to the resistance?to the resistance?

It increases by a factor of 2

When you rotate the knob of a light dimmer, what is being changed in the electric circuit?

The power and current (The voltage is provided at 120V from the outside. The light dimmer increases the resistance and therefore decreases the current that flows through the lightbulb)

Two lightbulbs operate at 120V, but one has a power rating of 25W while the other has a power rating of 100W. Which one has the greater resistance?

100W bulb (Since P=V²/R, the bulb with lower power rating has to have higher resistance)

Two space heaters in your living room are operated at 120V. Heater 1 has twice the resistance of heater 2. Which one will give off more heat?

Heater 2 will give off more heat, as it has lower resistance and therefore higher current, leading to greater power output.