Electric meters are instruments used to measure electrical values. The two most common meters are the ammeter (which measures ampere) and the voltmeter (which measures volts).The ammeter and voltmeter are variations of the galvanometer. Inside a galvanometer is a small magnet that sets up a magnetic field. This magnetic field generates a force that we can measure when current flows through a coil.
Below, the meter mechanisms are shown schematically.
The ammeter diverts electricity through a coil via a shunt (illustrated beneath the device), measuring the amount of current flowing through the circuit in amperes. It is connected in series, or directly in the line of the circuit. The voltmeter is connected in parallel, so that the light bulb falls between its two connections into the circuit. It is designed to measure potential differences. To ensure that it removes a minimum of current from the circuit, the voltmeter’s resistance (shown by the jagged black line beneath the device
Exercise
- Draw straight lines in your workbook that are of the following lengths:
- a) 150mm
- b) 0,025m
- c) 8,75cm
- d) 0,00019km
- e) 4m
- 2. Technician A says that 1 liter equals 1000 cubic centimeters. Technician B says the most versatile precision measuring instrument for an automotive technician is the vernier caliper.
Who is right?
- Technician A b. Technician B c. Both A and B d. Neither A nor B
- Technician A says that one revolution of the micrometer thimble equals 1⁄₄₀ inch. Technician
B says that one revolution of the micrometer thimble equals 0.025 inch. Who is right?
- Technician A b. Technician B
- Both A and B d. Neither A nor B
- Technician A says that the English system of measurement is based on the number 10.
Technician B says that calipers, dividers, and telescopic gauges are precision measuring instruments. Who is right?
- Technician A b. Technician B
- Both A and B d. Neither A nor B
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