Standardized Test Prep
Test-Taking Tip
Forming Operational Definitions
Some test questions ask you to apply an operational definition. Start by using details in the question as clues to help you recall the definition. The question below describes current direction and asks for the magnetic field direction. Then write what you recall about the definition. How is current defined? (flow of positive charge) Which hand do you use? (right hand) What points in the direction of the current? (thumb) What determines the magnetic field direction? (curl of fingers) Lastly, rule out choices that must be wrong. Responses A and B cannot be correct because the magnetic field is at right angles to the current.
Suppose a vertical wire is pushed through a hole in a horizontal tabletop. Current in the wire is directed into the plane of the tabletop from above. What is the magnetic field direction caused by this current, as seen from above?
into the plane of the tabletop
out of the plane of the tabletop
clockwise
counter-clockwise
left to right
(Answer: C)
Two solenoids are nested one inside the other. The inner solenoid is connected to a 12-V AC voltage source. The outer solenoid is part of a complete circuit. Will the setup function as a transformer?
No, there is no core.
No, there needs to be a ring.
No, both sides need a voltage source.
It is unclear, because current is not given.
Yes, AC induces a current in the outer coil.
What causes a ferromagnetic material to become magnetic?
unpaired electrons
paired electrons
unpaired protons
paired protons
none of the above
A transformer has 22 coils in its primary coil and 132 coils in its secondary coil. If the input voltage is 112 V, what is the secondary voltage?
6.00 V
18.7 V
222 V
266 V
672 V
The figure below is a transformer used in lighting dimmer switches. It has one coil wrapped around an iron core. Three moveable taps (T1, T2, and T3) are connected to the wire. When a tap is moved, the number of coils between that tap and the next tap changes. The coils between T1 and T2 form the primary coil. The coils between T2 and T3 form the secondary coil. To lower the output voltage for this transformer (to dim a light), how should one tap be moved?
Particle accelerators use electromagnets to change the direction in which charged particles travel. How does a charged particle move within a magnetic field?
It moves in the same direction as the magnetic field lines.
It moves in the direction opposite to the magnetic field lines.
It comes to a stop.
It moves in a direction perpendicular to the magnetic field lines.
none of the above
Is it possible for a magnetic field to slow down a charged particle moving through the field?
Yes, if the charge is moving perpendicular to the field at all times.
Yes, if the charge is moving in the direction of the magnetic field lines.
Yes, if the charge is moving in the direction opposite to the magnetic field lines.
Yes, if the charge is moving very slowly.
No, a magnetic field can only deflect a charged particle.
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