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The temperature in Philadelphia, PA can vary between 68.00 ° F and 100.00 ° F in one summer day. By what percentage will an aluminum wire’s resistance change during the day?

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When 100.0 V is applied across a 5-gauge (diameter 4.621 mm) wire that is 10 m long, the magnitude of the current density is 2.0 × 10 8 A/m 2 . What is the resistivity of the wire?

ρ = 5.00 × 10 −8 Ω · m

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A wire with a resistance of 5.0 Ω is drawn out through a die so that its new length is twice times its original length. Find the resistance of the longer wire. You may assume that the resistivity and density of the material are unchanged.

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What is the resistivity of a wire of 5-gauge wire ( A = 16.8 × 10 −6 m 2 ), 5.00 m length, and 5.10 m Ω resistance?

ρ = 1.71 × 10 −8 Ω · m

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Coils are often used in electrical and electronic circuits. Consider a coil which is formed by winding 1000 turns of insulated 20-gauge copper wire (area 0.52 mm 2 ) in a single layer on a cylindrical non-conducting core of radius 2.0 mm. What is the resistance of the coil? Neglect the thickness of the insulation.

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Currents of approximately 0.06 A can be potentially fatal. Currents in that range can make the heart fibrillate (beat in an uncontrolled manner). The resistance of a dry human body can be approximately 100 k Ω . (a) What voltage can cause 0.2 A through a dry human body? (b) When a human body is wet, the resistance can fall to 100 Ω . What voltage can cause harm to a wet body?

a. V = 6000 V ; b. V = 60 V

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A 20.00-ohm, 5.00-watt resistor is placed in series with a power supply. (a) What is the maximum voltage that can be applied to the resistor without harming the resistor? (b) What would be the current through the resistor?

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A battery with an emf of 24.00 V delivers a constant current of 2.00 mA to an appliance. How much work does the battery do in three minutes?

P = W t , W = 8.64 J

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A 12.00-V battery has an internal resistance of a tenth of an ohm. (a) What is the current if the battery terminals are momentarily shorted together? (b) What is the terminal voltage if the battery delivers 0.25 amps to a circuit?

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Challenge problems

A 10-gauge copper wire has a cross-sectional area A = 5.26 mm 2 and carries a current of I = 5.00 A . The density of copper is ρ = 89.50 g/cm 3 . One mole of copper atoms ( 6.02 × 10 23 atoms ) has a mass of approximately 63.50 g. What is the magnitude of the drift velocity of the electrons, assuming that each copper atom contributes one free electron to the current?

V = 7.09 cm 3 n = 8.49 × 10 28 electrons m 2 v d = 7.00 × 10 −5 m s

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The current through a 12-gauge wire is given as I ( t ) = ( 5.00 A ) sin ( 2 π 60 Hz t ) . What is the current density at time 15.00 ms?

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A particle accelerator produces a beam with a radius of 1.25 mm with a current of 2.00 mA. Each proton has a kinetic energy of 10.00 MeV. (a) What is the velocity of the protons? (b) What is the number ( n ) of protons per unit volume? (b) How many electrons pass a cross sectional area each second?

a. v = 5.83 × 10 13 protons m 3

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In this chapter, most examples and problems involved direct current (DC). DC circuits have the current flowing in one direction, from positive to negative. When the current was changing, it was changed linearly from I = I max to I = + I max and the voltage changed linearly from V = V max to V = + V max , where V max = I max R . Suppose a voltage source is placed in series with a resistor of R = 10 Ω that supplied a current that alternated as a sine wave, for example, I ( t ) = ( 3.00 A ) sin ( 2 π 4.00 s t ) . (a) What would a graph of the voltage drop across the resistor V ( t ) versus time look like? (b) What would a plot of V ( t ) versus I ( t ) for one period look like? ( Hint : If you are not sure, try plotting V ( t ) versus I ( t ) using a spreadsheet.)

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A current of I = 25 A is drawn from a 100-V battery for 30 seconds. By how much is the chemical energy reduced?

E = 75 kJ

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Consider a square rod of material with sides of length L = 3.00 cm with a current density of J = J 0 e α x k ^ = ( 0.35 A m 2 ) e ( 2.1 × 10 −3 m −1 ) x k ^ as shown below. Find the current that passes through the face of the rod.

Picture shows a co-ordinate axis with the square rod placed over it. It has dimensions of L in j and i directions. Current is flowing into the k direction through the area dx.
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A resistor of an unknown resistance is placed in an insulated container filled with 0.75 kg of water. A voltage source is connected in series with the resistor and a current of 1.2 amps flows through the resistor for 10 minutes. During this time, the temperature of the water is measured and the temperature change during this time is Δ T = 10.00 ° C . (a) What is the resistance of the resistor? (b) What is the voltage supplied by the power supply?

a. P = 52 W R = 36 Ω ; b. V = 43.54 V

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The charge that flows through a point in a wire as a function of time is modeled as q ( t ) = q 0 e t / T = 10.0 C e t / 5 s . (a) What is the initial current through the wire at time t = 0.00 s ? (b) Find the current at time t = 1 2 T . (c) At what time t will the current be reduced by one-half I = 1 2 I 0 ?

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Consider a resistor made from a hollow cylinder of carbon as shown below. The inner radius of the cylinder is R i = 0.20 mm and the outer radius is R 0 = 0.30 mm . The length of the resistor is L = 0.90 mm . The resistivity of the carbon is ρ = 3.5 × 10 −5 Ω · m . (a) Prove that the resistance perpendicular from the axis is R = ρ 2 π L ln ( R 0 R i ) . (b) What is the resistance?

Picture shows a cylinder of the length L. Internal radius is R1, external radius is R2.

a. R = ρ 2 π L ln ( R 0 R i ) ; b. R = 2.5 m Ω

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What is the current through a cylindrical wire of radius R = 0.1 mm if the current density is J = J 0 R r , where J 0 = 32000 A m 2 ?

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A student uses a 100.00-W, 115.00-V radiant heater to heat the student’s dorm room, during the hours between sunset and sunrise, 6:00 p.m. to 7:00 a.m. (a) What current does the heater operate at? (b) How many electrons move through the heater? (c) What is the resistance of the heater? (d) How much heat was added to the dorm room?

a. I = 8.69 A ; b. # electrons = 2.61 × 10 25 ; c. R = 13.23 Ω ; d. q = 4.68 × 10 6 J

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A 12-V car battery is used to power a 20.00-W, 12.00-V lamp during the physics club camping trip/star party. The cable to the lamp is 2.00 meters long, 14-gauge copper wire with a charge density of n = 9.50 × 10 28 m −3 . (a) What is the current draw by the lamp? (b) How long would it take an electron to get from the battery to the lamp?

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A physics student uses a 115.00-V immersion heater to heat 400.00 grams (almost two cups) of water for herbal tea. During the two minutes it takes the water to heat, the physics student becomes bored and decides to figure out the resistance of the heater. The student starts with the assumption that the water is initially at the temperature of the room T i = 25.00 ° C and reaches T f = 100.00 ° C . The specific heat of the water is c = 4180 J kg . What is the resistance of the heater?

P = 1045 W , P = V 2 R , R = 12.27 Ω

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Questions & Answers

A golfer on a fairway is 70 m away from the green, which sits below the level of the fairway by 20 m. If the golfer hits the ball at an angle of 40° with an initial speed of 20 m/s, how close to the green does she come?
Aislinn Reply
cm
tijani
what is titration
John Reply
what is physics
Siyaka Reply
A mouse of mass 200 g falls 100 m down a vertical mine shaft and lands at the bottom with a speed of 8.0 m/s. During its fall, how much work is done on the mouse by air resistance
Jude Reply
Can you compute that for me. Ty
Jude
what is the dimension formula of energy?
David Reply
what is viscosity?
David
what is inorganic
emma Reply
what is chemistry
Youesf Reply
what is inorganic
emma
Chemistry is a branch of science that deals with the study of matter,it composition,it structure and the changes it undergoes
Adjei
please, I'm a physics student and I need help in physics
Adjanou
chemistry could also be understood like the sexual attraction/repulsion of the male and female elements. the reaction varies depending on the energy differences of each given gender. + masculine -female.
Pedro
A ball is thrown straight up.it passes a 2.0m high window 7.50 m off the ground on it path up and takes 1.30 s to go past the window.what was the ball initial velocity
Krampah Reply
2. A sled plus passenger with total mass 50 kg is pulled 20 m across the snow (0.20) at constant velocity by a force directed 25° above the horizontal. Calculate (a) the work of the applied force, (b) the work of friction, and (c) the total work.
Sahid Reply
you have been hired as an espert witness in a court case involving an automobile accident. the accident involved car A of mass 1500kg which crashed into stationary car B of mass 1100kg. the driver of car A applied his brakes 15 m before he skidded and crashed into car B. after the collision, car A s
Samuel Reply
can someone explain to me, an ignorant high school student, why the trend of the graph doesn't follow the fact that the higher frequency a sound wave is, the more power it is, hence, making me think the phons output would follow this general trend?
Joseph Reply
Nevermind i just realied that the graph is the phons output for a person with normal hearing and not just the phons output of the sound waves power, I should read the entire thing next time
Joseph
Follow up question, does anyone know where I can find a graph that accuretly depicts the actual relative "power" output of sound over its frequency instead of just humans hearing
Joseph
"Generation of electrical energy from sound energy | IEEE Conference Publication | IEEE Xplore" ***ieeexplore.ieee.org/document/7150687?reload=true
Ryan
what's motion
Maurice Reply
what are the types of wave
Maurice
answer
Magreth
progressive wave
Magreth
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Muhammad Reply
fine, how about you?
Mohammed
hi
Mujahid
A string is 3.00 m long with a mass of 5.00 g. The string is held taut with a tension of 500.00 N applied to the string. A pulse is sent down the string. How long does it take the pulse to travel the 3.00 m of the string?
yasuo Reply
Who can show me the full solution in this problem?
Reofrir Reply
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Source:  OpenStax, University physics volume 2. OpenStax CNX. Oct 06, 2016 Download for free at http://cnx.org/content/col12074/1.3
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