Phys 101 Lecture 18

An electron is moving north in a region where the magnetic field is south. The magnetic force exerted on the electron is: 

• zero 
• up
• north
• south 

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A magnetic field exerts a force on a charged particle:

• always 
• never 
• if the particle is moving across the field lines
• if the particle is moving along the field lines 

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An electron travels due north through a vacuum in a region of uniform magnetic field  that is also directed due north. It will: 

• be unaffected by the field 
• speed up
• slow down
• follow a right-handed corkscrew path 

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An electron and a proton are both initially moving with the same speed and in the same direction at 90˚ to the same uniform magnetic field. They experience magnetic forces, which are initially: 

• identical
• equal in magnitude but opposite in direction 
• in the same direction and differing in magnitude by a factor of 1840 
• in opposite directions and differing in magnitude by a factor of 1840 

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A hydrogen atom that has lost its electron is moving east in a region where the magnetic field is directed from south to north. It will be deflected: 

• up
• down
• north 
• south

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what is the earths magnetic field useful for 

• deflecting the solar wind, charged particles that come from the Sun.
• wind
• sun
• light

What will happen when these magnets are brought close together?

• They will attract each other.
• They will repel each other.
• Both magnets will turn to the left
• Both magnets will turn to the right

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What is our best evidence that Earth has a magnetic field?

• All things fall toward Earth's center
• A compass needle lines up with it
• Winds blow from east to west
• Earth's oceans all have currents

Why does a compass needle point north?

• The compass is a bar magnet
• Because north is up
• Because it's magic
• It lines up with the Earth's magnetic field

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Where is the force of attraction the strongest on a magnet?

• at the poles
• in the middle
• above the magnet
• below the magnet

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