Question

name:
homework: wednesday
resistance = potential difference / current
r = v / i
units: r is measured in ohms (ω)
v is measured in volts (v)
i is measured in amperes (a)
solve the unknown measurement.
1.
i = 10 a
r = 1500 ω
v = ?
2.
i = ?
r = 200 ω
v = 240 v
3.
i = 15 a
r = ?
v = 110 v

1. what is the potential difference across an electrical load that has a resistance of 4ω and a current of 3a flowing through it?
2. calculate the current an electrical clothes dryer draws when it is connected to a 230 v source and has a resistance of 9.2ω.
3. what is the resistance in a circuit if a potential difference of 110 v causes a current of 10 a?

review questions:
a group of 8th grade students wants to find out how different surfaces affect how far a toy car rolls. the students build a ramp and place different surfaces at the bottom of the ramp, such as tile, carpet, and sandpaper. each time, they release the same toy car from the same spot at the top of the ramp without pushing it. they measure how far the car travels on each surface. the students use tile as their comparison surface.

1. independent variable:
2. dependent variable:
3. constants (at least 3):
4. control (comparison):

Explanation:

Ohm's Law Problems (Step-by-Step Format)

Step1: Rearrange for V

$V = I \times R$

Step1 Calculation (Q1):

$V = 10\ \text{A} \times 1500\ \Omega = 15000\ \text{V}$

Step2: Rearrange for I

$I = \frac{V}{R}$

Step2 Calculation (Q2):

$I = \frac{240\ \text{V}}{200\ \Omega} = 1.2\ \text{A}$

Step3: Rearrange for R

$R = \frac{V}{I}$

Step3 Calculation (Q3):

$R = \frac{110\ \text{V}}{15\ \text{A}} \approx 7.33\ \Omega$

Step4: Calculate V (Q4)

$V = 3\ \text{A} \times 4\ \Omega = 12\ \text{V}$

Step5: Calculate I (Q5)

$I = \frac{230\ \text{V}}{9.2\ \Omega} = 25\ \text{A}$

Step6: Calculate R (Q6)

$R = \frac{110\ \text{V}}{10\ \text{A}} = 11\ \Omega$

1. The independent variable is the factor intentionally changed to test its effect.
2. The dependent variable is the factor measured to observe changes from the independent variable.
3. Constants are factors kept identical across all trials to ensure a fair test.
4. The control is the standard condition used for comparison.

Answer:

(Ohm's Law Questions):

1. $V = 15000\ \text{V}$
2. $I = 1.2\ \text{A}$
3. $R \approx 7.33\ \Omega$
4. $12\ \text{V}$
5. $25\ \text{A}$
6. $11\ \Omega$

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Experimental Design Questions (Answer-Explanation Format)