QUESTION 20 Which of the following factors does not play a role in the formation of auroras near the geomagnetic north and south poles? a. The fact that air molecules emit light after being excited by subatomic particles b. The weak intensity of the magnetic field near either geomagnetic poles. O c. The increasing density of the atmosphere as charged particles penetrate more closely to the surface of the earth d. The solar wind e. The fact that the crust of the earth contains a relatively large percentage of ferromagnetic iron.

95. Select 1 answer.

5. The magnitude of the magnetic field around a single current-carrying wire with current I, Hol is given be B = where 4= 47 × 10-7 T·m/A. The formula for the force on a single 2πη current-carrying wire with current I, is F = ILB, if the current is perpendicular to the magnetic field. What is the magnitude of the force between two parallel wires, each carrying a 1A current, if the wires are 10 m long and 2 m apart.

Which scientist discovered that a compass can be deflected by a current-carrying wire?   a. Hans Oersted   b. Albert Einstein   c. Galileo Galilei   d. Sir Isaac Newton   e. Michael Faraday

1. Consider a beam of electrons that moves from the electron gun towards the screen of a cathode ray tube due to the potential difference of 15kV. A pair of coils are placed outside a cathode ray tube and produce a uniform magnetic field of 250 μT across the tube. Calculate the force experienced by the electrons if the magnetic field is in place: a. parallel with the direction of the beam. b. Perpendicular with the direction of the beam. c. 50 degrees with the direction of the beam.

CQ 10. Many roller coasters use magnetic brakes to slow the train at the end of its run. A conducting plate on the train passes by powerful magnets fixed on the track. a. Explain the principle behind this magnetic braking. b. The system needs an ordinary friction-based brake to bring the train to a full stop. Explain why the magnetic brake is not very efficient when the train is moving slowly

Describe the origins of the magnetic field of the Earth. Describe what is meant by magnetic field strength and state its unit of measurement in SI units. Select one or more: a. Magnetic field strength is measured in amperes per meter squared. b. О с. d. The magnetic field strength B is the value of the current in the loop per unit area. The magnetic field of the earth is caused by electric currents inside the molten iron core of the Earth. The magnetic field strength B is defined as the force acting per unit current in a wire of unit length when the wire is perpendicular to the magnetic field lines. e. The magnetic field of the earth is caused by Earth's rotation around the Sun. ☐ f. Magnetic field strength is measured in Tesla.