Electric Current Questions

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Science

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If 6.25 x 1018 electrons flow through a given cross-section per second, the current passing through the section is:

1 a

10 A

6.25 A

None of the above

An incandescent lamp is operated at 120 V, and the current is 0.5 A. So, the resistance of the lamp is:

120 Ω

60 Ω

24 Ω

240 Ω

A total charge of 16μC passes through a cross-sectional area of a nichrome wire in 4 s. How many electrons pass through the cross-sectional area in 16 s?

An electric heater operates on a household circuit at 120 V. The resistance of the heater wire is 12 Ω. What is the current passing through the heater wire? What is the power rating of the heater?

The operating potential difference of a light bulb is 120 V. The power rating of the bulb is
60 W. What is the current passing through the bulb’s filament? What is the resistance of the filament?

An electric iron of 500 W power is used daily for 30 minutes. If the cost per kW.h is $0.10, what is the weekly expense in using the electric iron??

Two resistors in series of resistance 6 Ω and 4 Ω are connected across a 12 V battery. What is the potential difference across 6 Ω resistor?

Several light bulbs, each of resistance 1.5 Ω, are connected in a series across a 120 V source of emf. If the current through the circuit is 2 A, how many light bulbs are there in the circuit?

Three resistors, 12 Ω, 18 Ω and 36 Ω, are connected in parallel. What is the equivalent resistance?

Two resistors of resistances 3 Ω and 6 Ω are connected in parallel across a 9 V battery. What is the equivalent resistance and the total current in the circuit?

Three resistors, each of resistance 6 Ω, are connected in such a way that that they form the three sides of a triangle. What is the equivalent resistance between any two vertices of the triangle? (picture attached)

Let n represent the number of similar resistors in a circuit. Each resistor has a resistance of r. When the resistors are connected in parallel the circuit has a total resistance of R. What would the total resistance of the circuit be if the resistors were instead connected in series?



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Explanation & Answer

The solution is attached.Please, let me know if you need further explanation.

Question 1
If 6.25 × 1018 electrons flow though a given cross-section per second, the current passing
through the section is:
Solution:
q = current × time
current =

q
time

1 electron charge = 1.602 × 10−19 C
∴ total charge, q = (6.25 × 1018 )(1.602 × 10−19 ) = 1.00125 C
∴ current =

1.00125 C
= 1.00125 A
1 sec

Answer: 1.00125 A (option A)

Question 2
An incandescent lamp is operated at 120 V, and the current is 0.5 A, the resistance of the lamp is:
Solution:
𝑉 = 𝐼𝑅
𝑅=

𝑉 120 𝑉
=
= 240Ω
𝐼
0.5 𝐴

Answer: 240 Ω (option D)

Question 3
A total charge of 16𝜇𝐶 passes through a cross-sectional area of a nichrome wire in 4 s. How
many electrons pass through the cross-sectional area in 16 s?
Solution:
Total charge that would pass through the wire in 16 s is:
∴ Total electron through the wire =
Answer: 3.995 × 1014 electrons

16×10−6 𝐶
4 𝑠𝑒𝑐

× 16 𝑠𝑒𝑐 = 64 × 10−6

...


Anonymous
Really helpful material, saved me a great deal of time.

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