Aproton beam in an accelerator carries a current of 130 μa. if the beam is incident on a target, how many protons strike the target in a period of 17.0 s?

The current intensity is the product between the total charge that flows through a certain point (in our case, the target) in a time interval :

We know the current, , and the time interval, , so we can find the total charge:


The total charge Q is the product between the number of protons N and the charge of each protons, e, which is :

we can  re-write the equation solving for N, so we can find the number of protons striking the target in 17 s:

Because the dept in the ocean