## Extra Credit 6

### Simple DC circuits

In this virtual laboratory you will use an on-line simulation from the University of Colorado PhET group to explore simple DC circuits.

Click the Lab icon.  Explore the interface!

• Components are dragged from the toolbox to make circuits.
• To explore the properties of a component, tap it.  You can then change many properties and also remove the component.

Record your measurements if prompted in blue font color.  You will need those values to answer the Extra Credit 6 questions on Canvas for up to 5 points extra Credit.

Experiments

Use one ideal battery (9 V, 0 Ω internal resistance), a light bulb (10 Ω) resistance) and  ideal wires (near 0 Ω resistance) to build the circuit shown on the right.  Make sure your light bulb lights up.

(a)  Use the voltmeter to measure the potential difference (ΔV) across the battery.  Record only the magnitude of the potential difference (omit +/- signs).  Make a similar potential difference measurement across the bulb and across each length of wire.  With the noncontact ammeter, measure the current through the bulb, IBulb.

Fill in the table below.

ΔVBattery ΔVwire A ΔVwire B ΔVBulb IBulb

Now use two ideal batteries (9 V, 0 Ω internal resistance), three light bulb (10 Ω) resistance) and as many ideal wires as needed to build several different circuits.

(b)  Use all the components (two batteries, 3 light bulbs) and connect them in such to produce the most light.  (The largest possible current should flow through the bulbs.  You can connect the batteries and bulbs in series or in parallel as needed.)

Make measurements and fill in the table below.

ΔVBattery IBattery ΔVany Bulb Iany Bulb

(c)  Use all the components (two batteries, 3 light bulbs) and connect them in such to produce the least amount of light or current, but not zero light or current.  (The smallest possible non-zero current should flow through the bulbs.)

Make measurements and fill in the table below.

ΔVBattery IBattery ΔVany Bulb Iany Bulb

Set up the circuit shown on the right with three 10 Ω bulbs and one 9 V battery.

(d)  Observe the brightness of the bulbs.

Make measurements and fill in the table below.

ΔVBattery IBattery ΔVBulb 1 IBulb 1 ΔVBulb 2 IBulb 2 ΔVBulb 3 IBulb 3

(e)  Change the internal resistance of the battery to 1 Ω.  What happens?

Make measurements and fill in the table below.

ΔVBattery IBattery ΔVBulb 1 IBulb 1 ΔVBulb 2 IBulb 2 ΔVBulb 3 IBulb 3

Now go to Canvas, Assignments, Extra Credit 6 and answer questions 1 - 5.  You can submit twice and the highest score counts.