Mastering Physics: PhET Tutorial: Circuit Construction Kit – Ohm’s Law and Power

Mastering Physics: PhET Tutorial: Circuit Construction Kit - Ohm's Law and Power

Part A

Question: Drag a battery into the construction panel, and use the voltmeter to determine which end of the battery is the positive terminal. The positive terminal has a higher potential than the negative terminal (recall that the voltmeter measures the potential difference between the red probe and the black probe).Which end of the battery is the positive terminal?

Answer:  the black end

Part B

Question: Construct a circuit containing one battery, one resistor, and wire to close the circuit. The order and orientation doesn’t matter, but it should look something like the figure below. You can show the values of the components by right-clicking (control-clicking) on each component and selecting Show Value in the pop-up menus. Use the default values of the battery and resistor.The figure shows a circuit that contains a 9.00-volt ideal battery, a resistor of 10.00 ohms, and a wire to close the circuit. Small blue balls are shown along the circuit inside its parts.You should see the blue electrons flowing through the circuit.In what direction is the current flowing through the circuit? Recall that current is the flow of positive charge.

Answer: The current flows from the positive terminal, through the wires and resistor, and into the negative terminal.

Part C

Question: Use the noncontact ammeter to measure the current flowing through the circuit.What is the current?

Answer:  0.9 A

Part D

Question: For the circuit in the previous part, the current flowing in the wire between the positive terminal of the battery and the resistor is ___________ the current flowing between the resistor and the negative terminal of the battery.

Answer: equal to

Part E

Question: Double the resistance of the resistor by changing it from 10 Ω to 20 Ω. What happens to the current flowing through the circuit?

Answer:  The current decreases by a factor of two.

Part F

Question: For the circuit containing one resistor and one battery, what happens to the current if the voltage is doubled?

Answer: The current increases by a factor of two.

Part G

Question: For the circuit containing one resistor and one battery, what happens to the current if the voltage is tripled and the resistance is doubled?

Answer: The current increases.

Part H

Question: What is the voltage reading across the resistor, as shown in the figure below?

Answer: 9.0 V

Part I

Question: A light bulb is basically a resistor that gets so hot that it glows, emitting light. For this tutorial we will assume the resistor in the light bulb is ohmic (that means Ohm’s law applies to the resistor).The rate of energy emitted by the light bulb is its output power, commonly referred to as luminosity (brighter means more luminous).Hook up a light bulb to a 5-V battery. Right-click (or control-click) on the light bulb, and change its resistance. How does the brightness of the light bulb depend on its resistance?

Answer: The light bulb gets dimmer as the resistance is increased.

Part J

Question: In Part H, you discovered that the luminosity of a light bulb increases if the current increases. The rate at which electric potential energy is converted into heat depends on the current flowing through the bulb and the voltage across the bulb. This energy is supplied by the battery. Mathematically, the luminosity P of the light bulb is given by P=ΔVI, where ΔV is the voltage across the bulb and I is the current.What happens to the luminosity of the light bulb if the voltage of the battery is doubled? (Note that the PhET simulation does not display a numerical value for the luminosity, so you should use the relationship between the luminosity, the voltage across the bulb, and the current.)

Answer: The luminosity increases by a factor of four.