Physics electricity lab

In summary, the resistance of a lit light bulb is different from when it is cold. To measure the resistance when the light bulb is on, a variable resistor can be used to approximate its value. The variable resistor is adjusted to obtain the same current as the light bulb with good batteries, and then its resistance is measured using an ohmmeter. This measurement is a valid approximation of the resistance of the light bulb when current is passing through it. The resistance is higher when the flashlight is off, as R and V are proportional when I is constant.
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Homework Statement


we wish to measure the resistance of a lit light bulb. Unfortunately, the resistance of the light bulb when hot is not the same as when it is cold. when the light bulb is turned on it becomes hot. we cannot easily measure the resistance of the light bulb when it is on (hot) because if we use an ohmmeter to measure the resistance when the light bulb is lit, we are really measuring the resistance of the whole circuit, not that of the light bulb only. however, we can approximate its value by replacing the light bulb with a variable resistor. adjust the variable resistor to obtain the same value of the current measured with the good batteries. Now disconnect the variable resistor from the circuit and measure its resistance using an ohmmeter. also, measure the resistance of the cold light bulb with the ohmmeter using the same connection.

The question is... you measured the resistance of the flashlight when it had no current passing through it. the resistance of the flashlight is different, however, when current is passing through it. explain how your measurement of the resistance of the variable resistor is a valid approximation of the resistance of the flashlight when it had current passing through it. is the resistance higher when the flashlight is on or off?

Homework Equations


V=IR


The Attempt at a Solution


I'm confused about the variable resistor part. But I believe resistance is higher when the flashlight in off because R and V are inversely proportional
 
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  • #2
natash said:
I'm confused about the variable resistor part. But I believe resistance is higher when the flashlight in off because R and V are inversely proportional

Actually, R and V are proportional, given the same current: V = I*R. I becomes the constant of proportionality.

If you did the lab then you should have actual values for the on-resistance and off-resistance that you can compare.
 

What is the purpose of a physics electricity lab?

The purpose of a physics electricity lab is to allow students to explore and experiment with the principles and laws of electricity in a hands-on way. This helps students better understand and retain the concepts being taught.

What are some common experiments in a physics electricity lab?

Some common experiments in a physics electricity lab include building simple circuits, measuring current and voltage, and investigating the effects of resistors and capacitors on a circuit.

What safety precautions should be taken during a physics electricity lab?

Safety is of utmost importance in a physics electricity lab. Students should always wear safety goggles, avoid touching live wires, and never work with electricity near water. It is also important to always have a teacher or lab supervisor present.

What skills can be developed in a physics electricity lab?

A physics electricity lab can help students develop critical thinking, problem-solving, and data analysis skills. It also allows students to practice using scientific equipment and following experimental procedures.

How can a physics electricity lab be made more engaging?

To make a physics electricity lab more engaging, teachers can incorporate real-life applications and examples, allow students to design their own experiments, and use interactive simulations and digital tools to enhance the learning experience.

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