Question

1. Which of the following, if doubled, would have an effect on the current through a conductor?

a. The number density (n) of mobile charge carriers
b. The drift speed of the mobile charge carriers
c. The charge on the mobile charge carriers
d. All of the above

2. Which of the following would have an effect on the resistance of a conducting wire?

a. The emf of the battery to which the resistor is connected
b. The current passing the through the conductor
c. The manner in which it is connected to other resistors
d. The material from which the wire is made.

3. Two identical 5Ω resistors and a 10Ω resistor are connected in a circuit. Which of the following cannot be the effective resistance of these resistors?

a. 20 Ω
b. 12.5 Ω
c. 8.3 Ω
d. 17.5 Ω

Answer 1

1)

I = v*n*e*A

curetn depends on drift speed (v)

charge of mobile carrier(e)

number density (n)

All of the above

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2)

resistance of wire R = rho*L/A

rho = resistivity depends on material

OPTION ( d)

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3)

R1 = 5

R2 = 5

R3 = 10

R1 , R2 , R3 area in series

Req = R1 + R2 + R3 = 5 +5 +10 = 20

R1 ,R2 R3 are in parallel

1/Req = 1/5 + 1/5 + 1/10

Req = 2

R1 , R2 are parallel and connested to R3 in series

Req = (R1*R2)/(R1+R2)+R3

Req = (5*5)/(5+5) + 10 = 12.5

R1 , R3 are in parallel and in series with R2

Req = (R1*R3)/(R1+R3) + R2

Req = (5*10)/(5+10) + 5 = 8.3

therefore 17.5 cannot be effective resistance of these resistors

option (d)