4/21/15 - Batteries, Bulbs, and Resistors - Circuits Cont.

So today we start off with a simple circuit and we attempt to predict what will happen when the switch in the middle is closed. We predicted that the center bulb would light up and the other two would grow dimmer.

As shown by the picture, the center bulb did nothing when the circuit was completed. Further explanation is present at the next picture.

We concluded the reason the second bulb had not lit due to the fact that the potential difference at the middle branch was zero. All potential was used by the top bulb and and potential given by the lower battery went to the lower bulb.

Next, we have a more complex circuit, the middle branch is removed and a third batter is added with an open switch in between.

Here is a drawing representing the circuit we were shown. We predict that the lower bulb will do nothing since there is no change to the potential difference and the upper will be brighter due to the extra power flowing through.

No surprise that the lower bulb had stayed the same, but the upper bulb had also remained unchanged.due to the potential difference being the same after the switch was turned on and the circuit was completed. There was change in potential due to the fact the batteries had provided the same voltage due to the first circuit being in series.

Our next exercise had up set up various configurations of bulbs and batteries. We made a chart (above) based on what we had discovered.

Batteries in series, bulbs in parallel makes bright. 

Batteries in series, bulbs in series makes dim.

Batteries in parallel, bulbs in series makes faint.

Batteries in parallel, bulbs in parallel makes dim.

Since the only things changing in these runs are the potential difference and current, we conclude that the brightness of the bulb is dependent on the power output.

In the end, we found we could get different power outputs out of the bulbs based on the circuit we put them in.

Here we measure the Ohms of some cheap resistors in class. We measure the amperage and potential difference in a circuit with a battery and resistor with a multi-meter and record the data on the whiteboard.

We measure the resistors in series and found that each resistor uses half the potential difference in the circuit. This allows the potential difference to return to zero by the end and the power is dissipated through the resistors.

We then hooked up the mutli-meter in series with the resistors to find the amperage along the circuit. To no one's surprise, the current is constant throughout the circuit in all cases.

The next circuit has the resistors in parallel.

We found the the potential difference is the same throughout the before and after both resistors.

However, the current is split between the resistors.

We then learned how to read resistors, and were given some antiques to practice with. We learned that the colours on tell us the Ohms of a resistor with a tolerance also depicted on the resistor. We calculated values then measured with a multi-meter to find that all are withing tolerance range.

We then took our three resistors from before and found them to all have the same value. We then hooked them up in series and found their total resistance.

Next we found the resistance if they were in parallel..

Here we're given a problem to work out and show all steps of simplification. We combine the resistors in series and parallel to find the total resistance.

Resistors in Series - Add Normally

Resistors in Parallel - Add Inverses