1) In each case, charged particles are in a magnetic uniform magnetic field. All
ID: 1437653 • Letter: 1
Question
1) In each case, charged particles are in a magnetic uniform magnetic field. All magnetic fields have the same strength and all point out of and are perpendicular to the page. In cases B through E, the velocity vectors are either horizontal or vertical, while in case F it makes a 45o angle with the +x and +y axes. The +x axis points horizontally to the right and the +y axis points vertically up the page (not out of the page).
In which situation or situations, does the magnetic force exerted by the field on the point charge have a component perpendicular to the page?
A.) None of them
B.) 5 of them
C.) 3 of them
D.) All of them
E.) 2 of them
F.) 4 of them
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2) The circuit shows a battery with three identical bulbs (meaning the bulbs have identical resistances). The brightness of each bulb depends on the magnitude of the current through it.
Does cutting the wire increase or decrease the brightnesses of A, B and C?
A.) A: increase B: increase C: increase
B.) A: decrease B: decrease C: increase
C.) A: increase B: decrease C: increase
D.) A: decrease B: increase C: decrease
E.) A: decrease B: increase C: increase
F.) A: increase B: increase C: decrease
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The eight circuits below all have one battery and three light bulbs. All of the batteries are identical.
The bulbs can have different resistances, given in units of ohms (). The specific values for these resistances are given in the figures. One of the three bulbs in each circuit is designated by an X. All of the wires in these circuits are identical and of equal length.
Which circuit(s) contains a bulb marked X with the smallest voltage drop across it?
A.) B
B.) G and H
C.) F
D.) A
E.) D
F.) E
Explanation / Answer
(1)
the direction of the magnetic force on a charged particle depends on the vector product of velocity vector and magnetic field vector.
The magnetic force on a charged particle is,
F=q (v bar x B bar)
the direction of the force is perpendicular to the plane which contains both the velocity vector and magnetic field vector. In all cases, magnetic field is out of the page. so, the magnetic force never be points along the same direction of the field. therefore, option (a) is correct.
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