Question

Two points along a wire are labeled Xand Y. The current is measured to be iXY= –3A.The reference direction of iXY is defined by double-subscript notation. a. In which direction are electrons flowing? From X to Y, or from Y to X? b. How much charge (in coulombs) passes through a cross section of the wire in 5 seconds?

Answer 1

Answer:

a. From Y to X

b. q = 15 C

Explanation:

a.

When current is denoted by double subscript, it is interpreted as traveling from 1st subscript to the second, when the value of current is positive. On the other hand, if the value of current is negative, then it means that the current is traveling from 2nd subscript to the 1st subscript. Since, the value of current is negative in the given question, therefore, it means that the current is traveling from 2nd subscript to the 1st subscript. Hence the direction of current or the flow of electrons is:

From Y to X

b.

Using the following formula of current:

I = q/t

where,

I = Current (Absolute Value) = 3  A

q = amount of charge = ?

t = time taken = 5 s

Therefore,

3 A = q/5 s

q = (3 A)(5 s)

q = 15 C