Learning Materials
Features
Discover
Chapter 18: Q12Q (page 755)
What is the difference between emf and electric potential difference?
Emf is the total energy provided to each mobile charge by the battery and potential energy is the energy lost by the charges while moving through a particular section of the circuit.
Over 30 million students worldwide already upgrade their learning with 91影视!
All the tools & learning materials you need for study success - in one app.
Get started for free
In the circuit shown figure 18.108, two thick copper wires connect a 1.5 V battery to a Nichrome wire. Each thick connecting wire is 17 cm long and has a radius of 9 mm. Copper has mobile electrons per cubic meter and electron mobility. The Nichrome wire is 8 cm long and has a radius of 3 mm. Nichrome has mobile electrons per cubic meter and electron mobility of .
(a) What is the magnitude of the electric field in the thick copper wire?
(b) What is the magnitude of the electric field in the thin Nichrome wire?
In a table like the one shown, write an inequality comparing each quantity in the steady state for a narrow resistor and thick connecting wires, which are made of the same material as the resistor.
Electron current in resistor | <,=, or > | Electron current in Thick Wires |
nR | nw | |
AR | Aw | |
uR | uw | |
ER | Ew | |
vR | vw |
In the circuit shown in Figure 18.87, bulbs 1 and 2 are identical in mechanical construction (the filaments have the same length and the same cross-sectional area), but the filaments are made of different metals. The electron mobility in the metal used in bulb 2 is three times as large as the electron mobility in the metal used in bulb 1, but both metals have the same number of mobile electrons per cubic meter. The two bulbs are connected in series to two batteries with thick copper wires (like your connecting wires).
(a)In bulb 1, the electron current is and the electric field is . In terms of these quantities, determine the corresponding quantities and for bulb 2, and explain your reasoning.
(b)When bulb 2 is replaced by a wire, the electron current through bulb 1 is and the electric field in bulb 1 is . How big is in terms of ? Explain your answer, including explicit mention of any approximations you must make. Do not use ohms or series-resistance equations in your explanation, unless you can show in detail how these concepts follow from the microscopic analysis introduced in this chapter.
(c)Explain why the electric field inside the thick copper wires is very small. Also explain why this very small electric field is the same in all of the copper wires, if they all have the same cross-sectional area.
(d)Figure 18.88 is a graph of the magnitude of the electric field at each location around the circuit when bulb 2 is replaced by a wire. Copy this graph and add to it, on the same scale, a graph of the magnitude of the electric field at each location around the circuit when both bulbs are in the circuit. The very small field in the copper wires has been shown much larger than it really is in order to give you room to show how that small field differs in the two circuits.
The drift speed in a copper wire is for a typical electron current. Calculate the magnitude of the electric field inside the copper wire. The mobility of mobile electrons in copper is . (Note that though the electric field in the wire is very small, it is adequate to push a sizable electron current through the copper wire.)
Compare the direction of the average electric field inside a battery to the direction of the electric field in the wires and resistors of a circuit.
What do you think about this solution?
We value your feedback to improve our textbook solutions.
Explanations 
Textbooks 
Flashcards 
91影视 AI 
Notes 
Study Plans 
Study Sets 
Find a degree 
Magazine