Close the switch such that the circuit is turned on. (You...

Close the switch such that the circuit is turned on. (You can also select the Values check box.) 4) What does the voltmeter read, $\Delta V = ...$? This represents the difference in the voltage between the red tip and the black tip of the Voltmeter. What does the ammeter read, $I = ...$? Using these values, and assuming that the only resistance in this circuit is due to the bulb's resistance, calculate the resistance of the light bulb; $R = ...$? (Always include units!) Also, draw this circuit as a circuit diagram using the proper circuit diagram symbols (See Ch. 23.1 in the textbook), showing the correct placement of the Ammeter and Voltmeter. 5) Using these same \"measured\" values, also calculate the power being used by the bulb. 6) Now flip the batteries around again. What happens to the reading on the Voltmeter?

Transcript

00:01 All right, we got a circuit in this problem, and we're asked just a bunch of quick questions, comparing different parts of the circuit.

00:10 We're told that this switch is initially open, that switch right there, and we're told to assume that everything is ideal.

00:20 So the first question we want to answer is, went the switch open, compare the current flowing in the two am meters, one and two.

00:30 If we follow the current from our power source here from the like a battery it's going to go up here from the positive here this way around the circuit and then and then it can't go through the open switch so the only path is down here through bulb b like this and then back to the negative end okay so the current all of the current has to flow through both of those ames meters there's nowhere where it forks so they both get the full amount of current so with the switch open i1 versus i2 they have equal currents that's our first okay let me get rid of my current direction the next set of questions are all what happens after we close the switch so let's go ahead and draw this now with the switch closed and i'll make it blue to match like that perfect now the current can fork, but you'll notice we actually have a short circuit here.

01:41 So same, it'll start going this way, it'll go through that wire, and then here is a path with no resistance back to the negative end of our battery.

01:51 Versus bulb b is going to give resistance.

01:53 So we basically short -circuited, so we're going to have no current flowing through bulb b.

01:59 It's as if it wasn't there.

02:00 The current says, i have a path of zero resistance.

02:03 All the current is going to take that path.

02:06 So the total resistance of the circuit now is just coming from bulb a, none from bulb b, whereas before the current had to go through bulb a and b in series and their resistance added.

02:20 So the total resistance of the circuit decreases because now it's only flowing through one bulb instead of two.

02:26 The brightness of the bulbs, well, bulb a is definitely going to increase its brightness.

02:33 A increases, because it's getting all the current now.

02:36 But b is going to turn off.

02:38 There's no current going through bulb b...

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