Electric Energy Potential and Capacitors

[neshepard]

Homework Statement

So this is from a past test put up as a study guide, but I'm stumped here. The question is:

A spark jumps between two electrodes, transferring a charge of 5 μC in 2 × 10−3 s. The
constant current I that would transfer the same charge in the same time is

The Attempt at a Solution

The solution is 2.5e-3A.

What is the formula to use? Is this to be treated as a capacitor therefore U=1/2QC? Just need a nudge to get my head around it for the test Tuesday.

Thanks

 

[PeterO]

Homework Statement

So this is from a past test put up as a study guide, but I'm stumped here. The question is:

A spark jumps between two electrodes, transferring a charge of 5 μC in 2 × 10−3 s. The
constant current I that would transfer the same charge in the same time is

The Attempt at a Solution

The solution is 2.5e-3A.

What is the formula to use? Is this to be treated as a capacitor therefore U=1/2QC? Just need a nudge to get my head around it for the test Tuesday.

Thanks

It is not a formula you need, it is contemplation of units.

Current is usually quoted in amperes, which means 1 Coulomb per second.
this spark involved much less that 1 Coulomb, but transferred in much less than a whole second. Think about it.

[Or use I = Q/t if you must]

 

[neshepard]

Thanks. I can never remember the various SI units for things. I end up sticking to Amp, Volt, etc, and this seems to be the down fall of my understanding. But they just don't stick. Anyway, I know the time was fast, and would play a key part, but not where.

Cheers