Suppose an electron e− is headed at us from outer space (a “cosmic ray”) in the direction shown. Which way will the earth’s magnetic field deflect it?
North
South
East
West
Suppose a dust cloud over our heads has acquired a positive charge via friction and is drifting from west to east. Which way will the magnetic force act on the dust cloud, assuming earth’s magnetic field is parallel to the surface.?
Up
Down
Which direction does the magnetic field produced by the left magnet point at the position of the right magnet?
←−
↑
−→
↓
Torque: clockwise; potential energy : positive
Torque: clockwise; potential energy : negative.
Torque: counter-clockwise; potential energy : positive.
Torque: counter-clockwise; potential energy : negative.
Which atomic quantity predominantly determines the magnetic properties of a material?
Atomic mass
Electron angular momentum
Atomic weight
Interatomic spacing
How could one demagnetize a piece of iron? Choose the best answer.
Heat it up
Hit it several times with a hammer
Either one
Neither one
The diagram (from Littlefuse, Inc.) above shows a solenoid that is used in an electromagnetic switch (a “relay”).. When the electrical switch at top is closed, the voltage at point 2 becomes positive while the voltage at point 3 remains at 0. Which way does the magnetic field inside the solenoid point?
Out of the page
up
Into the page
Referring to the same diagram, the upside-down T-shaped object (“plunger”) develops a sufficiently strong magnetic dipole moment after the solenoid is energized that it is pulled up into the solenoid (thus electrically connecting point 1 to point 4). After a period of repeated usage, the plunger’s dipole moment persists even with the solenoid de-energized. From this information we can deduce that the T-shaped object is made of a material that is?
Diamagnetic
Non-magnetic
Ferromagnetic
Paramagnetic
The circuit above consists of a resistor with R = 120 Ω, an inductor with L = 0.1 mH, a battery with E=12 V, and a switch. After being open for a long time, the switch is closed. What are good estimates for the current in the circuit 10−9 s and 10 s after the switch is closed.
10^−9 s: 0 mA; 10 s: 0 mA.
10^−9 s: 100 mA; 10 s: 0 mA.
10^−9 s: 0 mA; 10 s: 100 mA.
10^−9 s: 100 mA; 10 s: 100 mA.
The device pictured is called a “choke”. It’s nothing more than heavy gauge wire wound into a coil. Chokes are wired in series with sensitive electronic devices, usually very close to the “front end” connector. The most likely purpose of a choke is to?
Prevent large steady currents from flowing into a circuit.
Allow rapidly changing currents to pass into a circuit.
Block slowly varying currents from entering a circuit.
Keep high frequency AC current from entering a circuit.
Which pair of components wired in series can allow high frequency AC currents to flow through with moderate attenuation, but effectively block low frequency currents?
Resistor and Capacitor
Resistor and Inductor
Inductor and capacitor
A 0.4 H inductance solenoid wound with high quality copper wire consumes an average power of 0 W when connected by itself to a 170 V amplitude 60 Hz AC voltage source. This is because?
The RMS current through the solenoid is 0 A.
The RMS voltage across the solenoid is 0 V.
The phase between the solenoid’s current and voltage is 90 degrees
Resonance occurs in an AC circuit, from an electronics point of view, because the inductive reactance cancels the capacitive reactance. Another explanation for the resonance condition is that?
The circuit resistance drops to zero
The capacitance begins to dominate effects of the inductance.
The power supply drives current through the circuit at its natural frequency of oscillation.
The inductance begins to dominate effects of the capacitance.
Which pair of components wired in series can allow only a narrow range of "Goldilocks" frequency AC currents to flow through with moderate attenuation?
Inductor and Capacitor
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