Thanks! 1. The deflection of the electron beam on the end of a cathode ray tube

Question

Thanks!

1. The deflection of the electron beam on the end of a cathode ray tube is observed to be 2.4 cm when the potential difference across the deflecting plates is 68V. What will the deflection be when the potential difference is 49V if the accelerating voltage is the same?

A. 1.2 cm

B. 1.7 cm

C. 3.3 cm

D. 4.6 cm

2. A certain battery has an emf of 9.1V and an internal resistance of 1.5 ohms. If the battery is connected to resistors of 8.0 ohms and 24.0 ohms in parallel, what is the current through the battery?

A. 0.27 A

B. 1.2 A

C. 1.5 A

D. 7.5 A

Explanation / Answer

1) V1/d1 = V2/d2

Given that V1 = 68 V

d1 = 2.4 cm

V2 = 49 V

d2 = ?

d2 = (V2/V1)*d1 =
d2 = (49*2.4)/68
d2 = 1.7 cm

so correct option is 1.7 cm

2) fromula for terminal voltage across the battery is V = e-(i*r)

since the two resistors are connected in parallel

potential difference across resistors are same

net resistance is (R1*R2)/(R1+R2) = (8*24)/(8+24) = 6 ohm

potential drop across resistors is V = i*Rnet = 6*i

then 6*i = e-(i*r) = 9.1-(i*1.5)

7.5*i = 9.1

current i = 9.1/7.5 = 1.2 A

so the correct option is B.1.2 A

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