### Ohm's Law (MBL) Pre-lab Assignment

Print this page, record your answers on it, and show it to your lab TF at the start of your lab session. In this experiment you will investigate Ohm's Law by hooking up various circuits. In the lab you plot the current through a resistor versus the potential difference across it. We'll do something a little simpler here, using an ammeter to measure current and a voltmeter to measure potential difference.

Click the button to set up the simulation. You should see a circuit diagram with a 10-volt battery, a low-resistance ammeter, a 500 ohm resistor, and a high-resistance voltmeter. Don't worry about the large number of buttons, boxes, and assorted items you can drag into the circuit.

First, place your mouse on the ammeter (the circle with the A) and click the right mouse button. From the menu, click "Display Amperemeter" with the left mouse button. You should get a box showing the reading of the ammeter, which measures the current in the circuit. Now place your mouse on the voltmeter (the circle with the V) and click the right mouse button. From the menu, click "Display Voltmeter" with the left mouse button. You should get a box showing the potential difference across the resistor. Drag these boxes around the screen if they're covering things up.

1. Predict what the current (I) and potential difference (ΔV) readings would be if the resistance was set to 1000 ohms instead of 500 ohms. Briefly justify your predictions.
I = _______________ ΔV = _______________

Right-click on the resistor (the squiggly line) and select "Change Value". Enter 1000, hit "OK", and record the current and potential difference readings. If they differ from your predictions explain why.
I = _______________ ΔV = _______________

2. Now predict what the current and potential difference readings would be if there was a second 1000 ohm resistor in parallel with the first. Briefly justify your predictions.
I = _______________ ΔV = _______________

Left-click on the resistor icon in the menu on the right and, with the left mouse button held down, drag the mouse to the point on the circuit diagram halfway between the resistor and the voltmeter. Let the mouse button go, and a second resistor should appear in parallel with the first. What are the current and potential difference readings? If they differ from your predictions explain why.
I = _______________ ΔV = _______________

3. Predict what the current and potential difference readings would be if the second 1000 ohm resistor was in series with the first instead of in parallel. Briefly justify your predictions.
I = _______________ ΔV = _______________

Drag the second resistor with your mouse so it is connected in series with the first resistor. Placing it on top of the vertical red line below the first resistor should do this. What are the current and potential difference readings? If they differ from your predictions explain why.
I = _______________ ΔV = _______________