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Transcript
IPS: Unit 2.5 “I Just Couldn’t Resist Lighting Up Again” name _____________________ WHAT DO YOU THINK? What affects the amount of current passing through a circuit? a. __________________________________ b. __________________________________ c. __________________________________ d. __________________________________ How can you dim a light bulb? __________________________________________________________ ___________________________________________________________________________________ FOR YOU TO DO. 1. Wire the circuit pictured in the schematic at the right. Your teacher will give you a long piece of copper wire about one meter long. Measure the current passing through the circuit, the voltage gain of the battery, and the voltage loss of the bulb and the long copper wire. Current passing through the circuit: I = __________ Voltage gain of the battery VS = ____________ Voltage loss of the light bulb: VB = __________ Voltage loss of the copper wire: VCW = ___________ 2. Wire the circuit pictured in the schematic at the right. Your teacher will give you a long piece of nichrome wire to replace the copper wire used in #1. Make sure you spread out the wire so it does not touch itself. Measure the values shown. Current passing through the circuit: I = _____________ Voltage gain of the battery: VS = ____________ Voltage loss of the light bulb: VB = __________ Voltage loss of the nichrome wire: VNW = __________ IPS: Unit 3.5 1 4/30/2017 3. What happened to the current passing through the circuit in #2 compared to #1? 4. What happened to the voltage drop across the nichrome wire as compared to voltage drop across the copper wire? 5. What happened to the brightness of the bulb when the nichrome wire was used? 6. Which wire is a better conductor of electricity, the nichrome wire or copper wire? Think about this a little before you answer. 7. Which wire has more resistance? 8. What do we mean by resistance? 9. What is the unit for resistance 10. What is the schematic symbol for a resistor? ____________________________ 11. Complete the following table. A. Start with the circuit that you already wired with the long nichrome wire. B. Loosen the screw on the meter and shorten the nichrome wire so that it is one half its original length. C. Shorten the nichrome wire so that it is one quarter of its original length. D. Shorten the nichrome wire so that it is one eighth of its original length. 12. Length of wire Current - I amps Brightness of bulb Full 1/2 1/4 1/8 How does a dimmer switch work? 13. Now try a thin nichrome wire. How does it compare to the copper wire and thicker nichrome wire? __________________________________________________________________________________ 13. Take out the nichrome wire from your circuit and insert a dimmer switch to complete the circuit. Turn the knob on the dimmer switch and see what happens to the light bulb. 14. What is a rheostat (dimmer switch)? 15. a) What is the schematic symbol for a rheostat? b) Draw a schematic of a circuit with a battery, light bulb and a rheostat (dimmer switch). IPS: Unit 3.5 2 4/30/2017 PHYSICS TO GO. Ohm's Law Problems What is the equation for Ohm's Law? Write the equation in the memory circle at the right. Show the equation and your work to solve the following problems. 1. When a given light bulb is connected to the 120-volt outlet of a house a current of 0.4 amps passes through it. What is the resistance of the bulb? 2. When another, brighter bulb is also connected to the 120 volt outlet of a house a current of 1 amp passes through it. What is the resistance of this bulb? 3. When a toaster is plugged into the 120 volt of a house a current of 10 amps passes through it. What is the resistance of the toaster? 4. A hair dryer has a resistance of 8 ohms. How much current will pass through it when it is plugged into a 120-volt outlet? 5. What properties of a wire affect its resistance? How does each property affect the resistance? IPS: Unit 3.5 3 4/30/2017