WEBVTT physics/ap-physics-1-2/fullerton
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Hi everyone and welcome back to Educator.com.
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In this mini-lesson, we are going to go over page 1 of the APlusPhysics worksheet on Ohm's Law and you can find the link to that worksheet down below the video.
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Let us take a look at Number 1 -- Which graph best represents the relationship between the electrical power and the current in the resistor that obeys Ohm's Law?
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Well, power is current times voltage, so as current goes up, we would expect a linear increase in power.
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So the correct answer there must be Number 3.
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Number 2 -- A potential drop of 50 volts is measured across a 250 ohm resistor.
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What is the power developed in the resistor?
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Well, power is V²/R, so that will be 50 volts²/250 ohms or 10 W.
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The correct answer is Number 3.
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Looking at Number 3 -- How much electrical energy is required to move a 4 micro-coulomb charge through a potential difference of 36 volts?
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Well, the electrical energy or the work is charged times voltage, which will be 4 × 10^-6 micro-coulombs × 36 volts is going to work out to be right around 1.44 × 10^-4 J -- Answer is Number 3.
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Number 4 -- A circuit consists of a resistor in a battery.
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Increasing the voltage of the battery, while keeping the temperature of the circuit constant would result in an increase in...?
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Well, I = V/R. If the temperature is constant, then (R) should be constant if we increase the voltage, we should get an increase in current only, so the correct answer to 4 is Number 1.
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Number 5 -- A generator produces 115 volt potential difference in a maximum of 20 A of current.
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Find the total electrical energy the generator produces operating at maximum capacity for 60 seconds.
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We are looking for energy and we are given voltage and current.
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The way I would do this is realizing that power, which is W/t or E/t is also equal to current time's voltage.
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Therefore the energy (W) is going to be current × voltage × time or 20 A × 115 volts × 60 s, which is going to give us an energy of right around 138,000 J or 138 kJ.
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Moving on to Number 6 -- An electric circuit contains a variable resistor connected to a source of constant voltage.
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As the resistance of the variables that resistor has increased, the power dissipated does what?
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Power equals V²/R and our voltage is constant, so as the resistance is increased the power dissipated must decrease, so for Number 6 our correct answer is Number 1.
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Number 7 -- An electric circuit contains a variable resistor connected to a source of constant potential difference.
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Which graph best represents the relationship between current and resistance in that circuit?
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Current equals V/R by Ohm's Law and now we have a constant potential difference.
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What happens is resistance goes up and current must go down. Our answer there must be Number 1.
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One more -- Number 8 -- In a simple electric circuit a 24 ohm resistor is connected across a 6 volt battery.
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What is the current?
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Current equals V/R or 6 volts/24 ohms is going to be 0.25 A, so the correct answer is Number 2.
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All right. That completes page 1 of the worksheet on Ohm's Law.
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If this went well -- Terrific -- time to move on, but if you struggled with this a little bit, it is probably a good idea to go back and review the video, the lesson on Ohm's Law.
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Thanks so much for your time everyone and make it a great day!