Neets Module 16 Assignment 3

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1. What meters operate from their own power sources?
Self-excited.
2. What physical component of a galvanometer provides the restoring force for the coil?
Phosphor bronze ribbons.
3. In a galvanometer, what two methods are used to indicate the amount of coil rotation?
The pointer arrangement and the light and mirror arrangement.
4. What is the primary disadvantage of the pointer arrangement for indicating coil rotation?
Coil balance.
5. What component of the D�Arsonval meter movement completes the circuit for current flow to the coil?
Hairspring.
6. What component supplies restoring force to the coil of the D�Arsonval meter movement?
Hairspring.
7. What advantage is gained by using pole pieces with curved faces in the D�Arsonval meter movement?
Makes it possible to have a more linear scale than if the poles were flat.
8. What structurally large, low-resistance conductor is connected in parallel with the meter movement to prevent damage?
Shunt.
9. What type of temperature coefficient material does not produce increased heat in response to increased current flow?
Zero-temperature coefficient.
10. A good choice of shunt resistance will place the indicating pointer near what part of the meter scale with a normal load?
Midscale.
11. In what manner are current-measuring instruments connected to a circuit?
In series.
12. An ammeter should always be connected so that current will flow into what terminal and out of what terminal?
Negative, positive.
13. (True or False) The larger the current required to produce full-scale deflection of the meter coil, the better the sensitivity of the meter.
False.
14. What condition exists when the insertion of a meter into a circuit changes the operation of the circuit?
15. What modification is made to the D�Arsonval meter movement to enable the meter to measure voltage?
A multimeter (high resistance) is placed in series with the coil of the meter.
16. What factors determine the value of the multiplier resistor?
The current required for full-scale deflection, and the range of the voltage to be measured.
17. In what manner are voltage-measuring instruments connected to the circuit to be measured?
In parallel.
18. When making voltage measurements in a high-resistance circuit, you should always use a voltmeter with what relative value of resistance?
High.
19. What term is used to express the sensitivity of a voltmeter?
Ohms per volt.
20. What instrument is used for measuring the insulation resistance of cables?
Megohmmeter (megger).
21. What added features enable a dc milliammeter to function as an ohmmeter?
• A source of dc potential.
• One or more resistors (one of which is variable).
22. A full-scale deflection on an ohmmeter scale indicates what resistance between the leads?
Zero.
23. The R x 100 resistance selection on an ohmmeter has what amount of resistance compared to the R x 10 selection?
1/10.
24. What is the purpose of the guard ring in a megohmmeter?
Shunts leakage current, which prevents false readings.
25. Most meggers you will use are rated at what voltage?
500.
26. The development of excessive test voltages is avoided by the use of meggers equipped with what device?
Friction clutches.
27. What components in an electrodynamometer-type meter movement produce the magnetic field?
Fixed coils.
28. What is the limiting factor as to the amount of current an electrodynamometer meter movement can handle?
Size of spiral conducting.
29. What is the primary advantage of the electrodynamometer-type meter over the D�Arsonval-type meter?
The electrodynamometer-type meter can be used to measure both ac and dc currents.
 Author: CVN68 ID: 165471 Card Set: Neets Module 16 Assignment 3 Updated: 2012-08-09 20:38:17 Tags: Neets Folders: Description: Neets Show Answers: