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Magnetic Fields, Magnetic Forces, and Electromagnetic
Induction Sample Problems
- A wire 1 m long carries a current of 5 A. The wire is at right angles to a uniform magnetic field. The force on the wire is 0.2 N. What is the magnetic field strength?
- Now in number one, the wire is directed at an angle of 30°. What is the magnetic field strength?
- A 10 cm long wire is at right angles to a uniform magnetic field of 0.06 T. A 4 A current is in the wire. What magnetic force does it experience? What is the magnetic force if the wire was at an angle of 40° to the magnetic field?
- A beam of electrons travels at 3,000,000 m/s through a 0.04 T field. What force does the beam experience?
- Two currents (one of 2 A and the other of 4 A) are arranged parallel to each other, with the currents flowing in the same direction (assume they are flowing down in the plane of your paper). The wires are 3 m long and are separated by 8 cm. What is the net magnetic field at the midpoint between the two wires?
- Repeat number five, but now the currents are flowing in opposite directions (assume the wire carrying the 2 A is flowing down and the one carrying 4 A is flowing up in the plane of your papaer).
- Repeat number five. The wire carrying the 2 A current is to the right of the wire carrying 4 A. They are still separated by 8 cm (assume they are flowing down in the plane of your paper). What is the net magnetic field at a point 3 cm to the right of the wire carrying the 2 A current?
- A wire 2 m long moves perpendicularly through a 0.08 T field at a speed of 7 m/s. What emf is induced? Knowing Ohmís law and that the wire has a resistance of 0.50 ohms, what current flows?
- The direction of a 0.045 T field is 60° above the horizontal. A wire 2.5 m long moves horizontally through this field at 2.4 m/s. What is the vertical component of the magnetic field? What emf is induced in the wire?
- A transformer has input voltage and current of 12 V and 3 A. It has an output current of 0.75 A. If there are 1200 turns on the secondary, how many turns are on the primary? What is the input voltage?