# Two metallic wires A and B of the same material are connected in parallel. Wire A has length l and radius r. wire B has length 2l and radius 2r. Calculate the ratio of the equivalent resistance in parallel combination and the resistance of the wire A.

Wire A.

Length = l.

Area =pie r2.

R1= rho x l /pie r2.

Wire B.

Length = 2l.

Area = pie 4r2.

R2= rho x 2l/pie 4r2=rho x l /pie x 2r2.

total resistance.

1/Rp= 1/R1+1/R2.= pie r2/rho x l+2 pie r2/ rho x l.=3 pie r2/rho x l.

Rp= rho x l/ 3 pie x r2.

ratio = Rp/ R1= rho /3 pie r2divided by rho x l / pie x r2.

Rp / R1= 1 : 3.

Hope it helps you++++++++

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i think the answer is 1:8
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Two copper wires.A of length 1 and radius R and B of length 21 and radius 2r are connected in parallel find the ratio of the total resistance of parallel combination to the resistance of wire A.
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You are given three resistors of 10ohm, and 20ohm; a battery of emf 2.5 V , a key, an ammeter and a voltmeter. Draw a circuit diagram showing the correct connections of all given components such that voltmeter gives a reading of 2.0 V
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thx bro 1 like from me

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Cheers! • 16 • 7
Wire A. Length = l. Radius =r. Area =pie r2. R1= rho x l /pie r2. Wire B. Length = 2l. Radius = 2r. Area = pie 4r2. R2= rho x 2l/pie 4r2=rho x l /pie x 2r2. total resistance. 1/Rp= 1/R1+1/R2.= pie r2/rho x l+2 pie r2/ rho x l.=3 pie r2/rho x l. Rp= rho x l/ 3 pie x r2. ratio = Rp/ R1= rho /3 pie r2divided by rho x l / pie x r2. Rp / R1= 1 : 3.
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If I actually tell, Iam not able to understand the question
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Wire A. Length = l. Radius =r. Area =pie r2. R1= rho x l /pie r2. Wire B. Length = 2l. Radius = 2r. Area = pie 4r2. R2= rho x 2l/pie 4r2=rho x l /pie x 2r2. total resistance. 1/Rp= 1/R1+1/R2.= pie r2/rho x l+2 pie r2/ rho x l.=3 pie r2/rho x l. Rp= rho x l/ 3 pie x r2. ratio = Rp/ R1= rho /3 pie r2divided by rho x l / pie x r2. Rp / R1= 1 : 3.
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R=wire a /wire b. And put the formulae i.e.r=rho*l/a for both wires. Hope it helps........
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For a wire A, the resistance is RA with diameter D and length L. For another wire B of resistance RB, made of same element as A, the diameter is 2D and length is 4L. Find the ratio RB:RA
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1:3.
• 3
I think 1:3
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Like it • 1
I THINK 1:3
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