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A metal wire of resistance Ris cut into two pieces of equal length. The two pieces are connected together side by side. What is the resistance of the two connected wires?

Short Answer

Expert verified

The resistance of the two connected wires is Req=R4.

Step by step solution

01

Given Information

We have to find the resistance of the two connected wires.

02

Simplify

The resistance through the wire depends on the area and the resistivity ÒÏof the wire and the formula is given as

localid="1648650084630" R=ÒÏLA...(1)

Where, Lis the length of the filament, Ais the area and ÒÏis the resistivity of the material. As shown by equation (1), the resistance is directly proportional to the length

RαL

If the wire has length Land it is divided into two pieces, the length of each wire is L/2. The resistance will be halved as the length is halved, so it will be R/2for each wire.

As when both new wires are connected side by side, so they will be in parallel and this Equation shows the equivalent resistance for the parallel connection in the form

localid="1648650104413" 1Req=1R1+1R2+...+1RN...(2)

The two wires and each wire has resistance R/2, so we can get the equivalent resistance for the combination by using equation (2)in the form

1Req=1R1+1R21Req=1R/2+1R/2Req=4R-1

The equivalent resistance is Req=R4

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Most popular questions from this chapter

A 12 V car battery dies not so much because its voltage drops but because chemical reactions increase its internal resistance. A good battery connected with jumper cables can both start the engine and recharge the dead battery. Consider the automotive circuit of FIGURE P28.65.

a. How much current could the good battery alone drive through the starter motor?

b. How much current is the dead battery alone able to drive through the starter motor?

c. With the jumper cables attached, how much current passes through the starter motor?

d. With the jumper cables attached, how much current passes through the dead battery, and in which direction?

The tip of a flashlight bulb is touching the top of the 3Vbattery in FIGURE Q28.2. Does the bulb light? Why or why not?

The capacitor in FIGURE P28.73begins to charge after the switch closes atτ=0s..

a. What is ∆Vc a very long time after the switch has closed?

b. What isQmaxin terms of E,R, and C?

c. In this circuit, does localid="1649091794998" I=+dQ/dtor-dQ/dt? Explain.

d. Find an expression for the current I at time t. Graph I from Ï„=0to localid="1649091939933" t=5r.

The flash on a compact camera stores energy in a 120μFcapacitor that is charged to 220V. When the flash is fired, the capacitor is quickly discharged through a lightbulb with5.0Ωof resistance.

a. Light from the flash is essentially finished after two time constants have elapsed. For how long does this flash illuminate the scene?

b. At what rate is the lightbulb dissipating energy 250μsafter the flash is fired?

c. What total energy is dissipated by the lightbulb?

The circuit of FIGURE Q28.4 has two resistors, with R1>R2. Which of the two resistors dissipates the larger amount of power? Explain.

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