# Electromagnetism help

Hi

I am confused for electromagnetism I think electromagnetism will be the only thing stopping me from getting E. How and when do we use the right hand slap and grip rule and is it when the wire is parallel to the magnetic field there’s no force?

Kia ora,

I would recommend using the right hand slap rule whenever you know two of these things, and are trying to determine the third:

• the force experienced by a moving charge
• the direction of a magnetic field a charge is travelling through
• the initial direction of a charge that experiences a force due to a magnetic field

The right hand grip rule is used to show the direction of magnetic field lines around a current. It can also be used to determine which end of a solenoid (coil of wire) behaves as a north or south pole, but this isn’t assessed in NCEA L2 Physics exams.

Looking at the standard, you can see what can be assessed:

• force on a current carrying conductor in a magnetic field
• force on charged particles moving in a magnetic field
• induced voltage generated across a straight conductor moving in a uniform magnetic field.

You are correct, when charges (in or out of a wire) are moving parallel with magnetic field lines, no magnetic force is experienced by the charges. However, if a wire were moved across magnetic field lines, the charges within the wire would experience a magnetic force. The maximum force is experienced when the angle between the direction of movement of the charge, and the magnetic field lines, is 90 degrees.

I would recommend attempting some collated questions, such as those found on No Brain Too Small, and then check your answers.

If you have any other questions, or need clarification, please let me know.