Magnetic fields do not affect charges that are moving parallel to them. 

Thus, the magnetic force will be at a maximum when moving perpendicular to the field, and at zero when moving parallel to the field.

The centripetal force will need to be equal to the magnetic force.

Solving for

Converting:

Plugging in values:

We need to use the right hand rule to solve this problem. However, the right hand rule applies to the flow of current, which is in the opposite direction of the actual flow of electrons (current is defined, in this case, as the direction of proton flow). Therefore, you can either use the right hand rule and reverse what you determine, or simply use your left hand.

Let's just use our left hand. Point your thumb out and curl your fingers. Your fingers should be pointing at you. This is the direction of the electric field when electrons are traveling the direction of your thumb. If you lay your left thumb along the wire loop on the left side of the loop, our fingers are inside the loop and pointing out of the screen. This is the scenario we are looking for. Therefore, the electrons need to flow clockwise around the loop.

Note that the electrons must flow through the wire, eliminating the answer options for "into the screen" and "out of the screen."

Using the right hand rule, we can tell that the direction of the magnetic field due to the bottom wire is out of the screen. Likewise, we can tell that the magnetic field due to the top wire is into the screen. Because point R is halfway between the two wires, they each have the same strength. Therefore, they both cancel each other out, leaving no magnetic field.

Let's use the right-hand rule to determine the magnetic field cause by each current.

For current , we determine that the magnetic field is going into the screen.

For current , we determine that the magnetic field is going out of the screen.

Do the two directions cancel out? Well, the magnitude of  is greater than the magnitude of , meaning that  will overpower , so the net direction is out of the screen.

Recall that the convention for the direction of current is from the positive end of the voltage source to the negative end (opposite the direction of flow of electrons). Thus, in this circuit the current is flowing counterclockwise from the voltage source. Using the right hand rule for the conventional current in the wire, the right thumb is pointed along the wire pointing to the left. At point the fingers curl around and point up, out of the screen. This can be verified by putting the thumb in the direction of current anywhere in the circuit. For example, if we take the direction of the current across the resistor, our thumb points down. Curling our fingers around the wire, the fingers will again point out of the screen at point , verifying our initial answer.

Current flows counterclockwise in this circuit. Using the right hand rule for the conventional current in the wire, the right thumb is pointed along the wire pointing to the left at the top of the circuit. At point the fingers curl around and point down, into the screen.

The current flows through this circuit counterclockwise. Using the right hand rule for the conventional current in the wire, the right thumb is pointed along the wire pointing to the right in the wire at the bottom of the circuit. At point the fingers curl around and point down, into the screen.

Visualizing a globe and pointing the thump "south" towards the "north" magnetic pole shows that the fingers curl and point from east to west.

According to the right hand rule, counter-clockwise spinning charge would produce a field going out of the screen; however, because electrons are negatively charged, they produce an opposite field. Therefore, the field created by these electrons is going into the screen.