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In 1827, Georg Ohm discovered the relationship between current, potential difference, and resistance. This relationship became known as

**Ohm ’s Law**

.

**Question:**

How are potential difference (V), current (I), and resistance (R) related?

**Materials:**

PhET Circuit Construction Kit (DC only)

**Method:**

1.

2.

Figure 1

Use the data table given to record your findings.

Open the PhET Circuit Construction Kit (DC only). (Hint: google search “phet dc only”)

3.

Construct a simple circuit using 1 battery and 1 light bulb (see figure 1). The switch is optional.

4.

5.

Right-click on the battery and change its voltage to 15 V. Right-click on the light bulb and change its resistance to 50

S

.

Use the voltmeter and non-contact ammeter (under “Tools”) to measure and record

6.

7.

the potential difference (V) and current (I) across the light bulb. (Recall that potential difference is also know as

**voltage**

.)

Repeat steps 4 and 5 for the remaining battery and light bulb values.

Calculate the ratio (V÷I) for each pair of V and I values. Record your answers to a whole number.

Battery

15 V

30 V

45 V

100

50

75

100

50

75

100

Light Bulb

R (

S

)

50

Voltage

V (V)

75

*whole #*

Current

I (A)

*2 dec.pl.*

Ratio

(V÷I)

*whole #*

**Conclusion:**

Answer the initial question. Express your answer as a formula.

2.

3.

4.

**Analysis**

*(Be sure to use complete sentences for question 1 and GRESS for questions 2 to 4!)*

1. Compare the (V÷I) ratios to the light bulb R values.

(a) W hat do you notice? Why?

(b) W hat is this relationship known as?

A resistor is connected to a 36 V power supply. An ammeter measures a current of 2.0 A going through it. Determine the resistance of the resistor.

A computer adapter has a voltage of 18 V and a resistance of 4.0

S

. The adapter gets warm when operating. Determine the current going through the adapter.

Typical household circuits can carry a maximum current of 15 A. If a wire has a resistance of 8.0

S

, determine the voltage across the energy source.