A 898 W heating unit is designed to operate with an applied potential difference of 119 V. (a) By what percentage will its heat output Irop if the applied potential difference drops to 113 V? Assume no change in resistance. (b) If you took the variation of resistance vith temperature into account, would the actual drop in heat output be larger or smaller than that calculated in (a)? (a) Number i Units (b)

A 898 W heating unit is designed to operate with an applied potential difference of 119 V. (a) By what percentage will its heat output Irop if the applied potential difference drops to 113 V? Assume no change in resistance. (b) If you took the variation of resistance vith temperature into account, would the actual drop in heat output be larger or smaller than that calculated in (a)? (a) Number i Units (b)

University Physics Volume 2

18th Edition

ISBN:9781938168161

Author:OpenStax

Publisher:OpenStax

Chapter10: Direct-current Circuits

Section: Chapter Questions

Problem 25P: A 12.0-V emf automobile battery has a terminal voltage of 16.0 V when being charged by a current of...

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Power P0 = I0 V0 is delivered to a resistor of resistance R0. If the resistance is doubled (Rnew = 2R0) while the voltage is adjusted such that the current is constant, what are the ratios (a) Pnew/P0 and (b) Vnew/V0? If, instead, the resistance is held constant while Pnew = 2P0, what are the ratios (c) Vnew/V0, and (d) Inew/I0?
Power P0 = I0 V0 is delivered to a resistor of resistance R0. If the resistance is doubled (Rnew = 2R0) while the voltage is adjusted such that the current is constant, what are the ratios (a) Pnew/P0 and (b) Vnew/V0? If, instead, the resistance is held constant while Pnew = 2P0, what are the ratios (c) Vnew/V0, and (d) Inew/I0?
Resistors are commonly rated at 18W,14W,12W ,1 W and 2 W for use in electrical circuits. If a current of1 = 2.00 A is accidentally passed through a R=1.00 resistor rated at 1 W, what would be the most probable outcome? Is there anything that can be done to prevent such an accident?
A 12.0-V emf automobile battery has a terminal voltage of 16.0 V when being charged by a current of 10.0 A. (a) What is the battery’s internal resistance? (b) What power is dissipated inside the battery? (c) At what rate (in °C/min ) will its temperature increase if its mass is 20.0 kg and it has a specific heat of 0.300 kcal/kg • °C, assuming no heat escapes?
Lightbulb A is marked 25.0 W 120. V, and lightbulb B is marked 100. W 120. V. These labels mean that each lightbulb has its respective power delivered to it when it is connected to a constant 120.-V source. (a) Find the resistance of each lightbulb. (b) During what time interval does 1.00 C pass into lightbulb A? (c) Is this charge different upon its exit versus its entry into the lightbulb? Explain. (d) In what time interval does 1.00 J pass into lightbulb A? (e) By what mechanisms does this energy enter and exit the lightbulb? Explain. (f) Find the cost of running lightbulb A continuously for 30.0 days, assuming the electric company sells its product at 0.110 per kWh.
Review. When a straight wire is warmed, its resistance is given by R = R0,[1 + a(T T0)] according to Equation 27.20, where a is the temperature coefficient of resistivity. This expression needs to be modified if we include the change in dimensions of the wire due to thermal expansion. For a copper wire of radius 0.100 0 mm and length 2.000 m, find its resistance at 100.0C, including the effects of both thermal expansion and temperature variation of resistivity. Assume the coefficients are known to four significant figures.
A 500 W heating unit is designed to operate with an applied potential difference of 115 V. (a) By what percentage will its heat output drop if the applied potential difference drops to 110 V? Assume no change in resistance. (b) If you took the variation of resistance with temperature into account, would the actual drop in heat output be larger or smaller than that calculated in (a)?
(a) A well-insulated electric water heater warms 111 kg of water from 20.0°C to 45.0°C in 23.0 min. Find the resistance (in 0) of its heating element, which is connected across a 240 V potential difference. Enter a number. (b) What If? How much additional time (in min) would it take the heater to raise the temperature of the water from 45.0°C to 100°C? min (c) What would be the total amount of time (in min) required to evaporate all of the water in the heater starting from 20.0°C? min
In an automobile, the system voltage varies from about12 V when the car is off to about 13.8 V when the car is onand the charging system is in operation, a difference of15%. By what percentage does the power delivered to theheadlights vary as the voltage changes from 12 V to 13.8 V?Assume the headlight resistance remains constant.
How much electrical energy is transferred to thermal energy in 2.50 hrs by an electrical resistance of 500 ohms when the potential applied across it is 80.0V? Express your answer in kJ.
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A 120 V potential difference is applied to a space heater whose resistance is 17 Q when hot. (a) At what rate is electrical energy transferred to thermal energy? (b) What is the cost for 4.4 hat US$0.05/kW.h? (a) Number Units (b) Number i Units