Electronics-Magnetism and Electrom
Electronics-Magnetism and Electrom
1. Permeability is the inverse equivalent of which electrical term?
- Voltage
- Current
- Resistance
- Conductance
2. Which electromagnetic device uses brushes and a commutator?
- A speaker
- A dc generator
- A relay
- A solenoid
3. What is the flux density of a magnetic field whose flux is 3000 µWb and cross-sectional area is 0.25 m2?
- 12,000 mu.gifT
- 83,330 T
- 0 T
- More information is needed in order to find flux density.
4. What are the effects of moving a closed wire loop through a magnetic field?
- A voltage is induced in the wire.
- A current is induced in the wire.
- The polarity across the wire depends on the direction of motion.
- All of the above
5. The Hall effect
- is a phenomenon with no practical applications
- is used in various sensor applications
- can develop potentials of thousands of volts
- is the basis for solar cell operation
6. "Series" and "parallel" as applied to dc motors refer to
- the connection of the motor and controller
- the connection of the field coil and armature windings
- the connection of the brush and commutator
- the connection of the motor batteries
7. The component that produces power in an electromagnetic generator is called the
- armature
- field winding
- commutator
- brush
8. What is the magnetomotive force in a 150-turn coil of wire with 2 A flowing through it?
- 13.33 mAt
- 300 At
- 75 At
- 152 At
9. A Hall effect sensor
- exists only in theory
- is a noncontacting magnetic sensor
- can operate only a few times before failure
- produces very large voltages
10. Which two values are plotted on a B-H curve graph?
- Reluctance and flux density
- Permeability and reluctance
- Magnetizing force and permeability
- Flux density and magnetizing force