A cell has an emf of 2.5 V. It cannot be balanced on a potentiometer of length 100.0 cm when connected to a driver cell of 2.0V. Which of the following best explains why there is no balance point? A The current in the wire is too low. B The balance length is too smallI. C The emf of the cell is too low. D The voltage across the wire is too low.

A cell has an emf of 2.5 V. It cannot be balanced on a potentiometer of length 100.0 cm when connected to a driver cell of 2.0V. Which of the following best explains why there is no balance point? A The current in the wire is too low. B The balance length is too smallI. C The emf of the cell is too low. D The voltage across the wire is too low.

College Physics

1st Edition

ISBN:9781938168000

Author:Paul Peter Urone, Roger Hinrichs

Publisher:Paul Peter Urone, Roger Hinrichs

Chapter21: Circuits And Dc Instruments

Section: Chapter Questions

Problem 68PE: A 500- resistor, an uncharged 1.50-F capacitor and a 6.16-V emf are connected in series, (a) What is...

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(a) What is the unknown emfx in a potentiometer that balances when Rxis 10.0 O, and balances when Rsis 15.0for a standard 3.000-V emf? (b) The same emfx is placed in the same potentiometer, which now balances when Rsis 15.0for a standard emf of 3.100 V. At what resistance Rxwill the potentiometer balance?
Consider a series RC circuit as in Figure P28.38 for which R = 1.00 M, C = 5.00 F, and = 30.0 V. Find (a) the time constant of the circuit and (b) the maximum charge on the capacitor after the switch is thrown closed. (c) Find the current in the resistor 10.0 s after the switch is closed.
The label on a battery-powered radio recommends the use of a rechargeable nickel-cadmium cell (nicads), although it has a 1.25-V emf, whereas an alkaline cell has a 1.58-V emf. The radio has a 3.20 resistance.(a) Draw a circuit diagram of the radio and its battery. Now, calculate the power delivered to the radio (b) when using a nicad cells, each having an internal resistance of 0.0400 , and (c) when using an alkaline cell, having an internal resistance of 0.200 . (d) Does this differenceseem significant, considering that the radio's effective resistance is lowered when its volume is aimed up?
(a) What is the resistance of a lightbulb that uses an average power of 75.0 W when connected to a 60.0-Hz power source having a maximum voltage of 170 V? (b) What If? What is the resistance of a 100-W lightbulb?
(a) What is the resistance of a light bulb that uses an average power of 75.0 W when connected to a 60.0-Hz power source having a maximum voltage of 170. V? (b) What is the resistance of a 100.-W lightbulb?
A 20.00-V battery is used to supply current to a 10-k resistor. Assume the voltage drop across any wires used for connections is negligible, (a) What is the current through the resistor? (b) What is the power dissipated by the resistor? (c) What is the power input from the battery; assuming all the electrical power is dissipated by the resistor? (d) What happens to the energy dissipated by the resistor?
Figure P29.60 shows a simple RC circuit with a 2.50-F capacitor, a 3.50-M resistor, a 9.00-V emf, and a switch. What are a. the charge on the capacitor, b. the current in the resistor, c. the rate at which the capacitor is storing energy, and d. the rate at which the battery is delivering energy exactly 7.50 s alter the switch is closed?
Integrated Concepts (a) What energy is dissipated by a lightning bolt having a 20,000-A current, a voltage of 1.00102 MV, and a length of 1.00 ms? (b) What mass of tree sap could be raised from 18.0°C to its boiling point and then evaporated by this energy, assuming sap has the same thermal characteristics as water?
Unreasonable Results (a) What current is needed to transmit 1.00 102 MW of power at 10.0kV? (b) Find the resistance of 1.00 km of wire that would cause a 0.0100% power loss. (c) What is the diameter of a 1.00-km-long copper wire having this resistance? (d) What is unreasonable about these results? (e) Which assumptions are unreasonable, or which premises are inconsistent?
As in Example 27.2, consider a power supply with fixed emf and internal resistance r causing current in a load resistance R. In this problem, R is fixed and r is a variable. The efficiency is defined as the energy delivered to the load divided by the energy delivered by the emf. (a) When the internal resistance is adjusted for maximum power transfer, what is the efficiency? (b) What should be the internal resistance for maximum possible efficiency? (c) When the electric company sells energy to a customer, does it have a goal of high efficiency or of maximum power transfer? Explain. (d) When a student connects a loudspeaker to an amplifier, does she most want high efficiency or high power transfer? Explain.
A 500- resistor, an uncharged 1.50-F capacitor and a 6.16-V emf are connected in series, (a) What is the initial current? (b) What is the RC time constant? (c) What is the current after one time constant? (d) What is the voltage on the capacitor after one time constant?
In the circuit of Figure P27.25, the switch S has been open for a long time. It is then suddenly closed. Take = 10.0 V, R1 = 50.0 k, R2 = 100 k, and C = 10.0 F. Determine the time constant (a) before the switch is closed and (b) after the switch is closed. (c) Let the switch be closed at t = 0. Determine the current in the switch as a function of time. Figure P27.25 Problems 25 and 26.