# Homework Help: Direction of magnetic field in antenna

1. Aug 14, 2011

### sparkle123

In the middle picture, since the current is directed downward (I think), by the right hand rule shouldn't the magnetic field lines be clockwise?
Thanks!

2. Aug 14, 2011

### cmb

'Positives' (conventional charge) looks like it is flowing up into the top element, and up out of the bottom element ('leaving behind' a -ve charge), just like the arrows show. No?

3. Aug 14, 2011

### sparkle123

Thanks!
but the purple arrows I(t) are flowing down?
Also, I'm not sure if the current can flow down the conductors through empty space...

4. Aug 14, 2011

### I like Serena

Hi sparkle123!

No the current does not flow through empty space.
The purple arrow from the plus pole continues its flow into the upper rod where it dead-ends, resulting in a increasingly positive charge.
In the upper rod the current flows up.

Similarly, charge from the lower rod is sucked into the battery, resulting in a current flowing up in the lower rod.

These flows cannot continue indefinitely, since the charge has nowhere else to go.
So soon after the current starts flowing, the current diminishes until it is zero.

5. Aug 14, 2011

### sparkle123

Thanks I like Serena! :) That makes so much more sense!
I wish the textbook explained it the way you did - it just says that when the rods are fully charged, the current is zero.

6. Aug 14, 2011

Thanks!