Resistors

A wattmeter is used to measure the value of power. It is connected to the circuit directly. A wattmeter consists of coils: two fixed coils and a coil which moves in the magnetic field produced by the fixed coils. Wire used for the coils must have a high resistance; the fixed coils are in series with the load, the moving coil is connected across the line in series with a resistance. When a wattmeter is used, the readings on its scale show the value of power being used.
Answer the following questions:

1. What is the text about? 2. What is the wattmeter used for? 3. What does it consist of? 4. In what way are the elements connected? 5. What do the readings on the scale show?
Rheostat
A rheostat is a resistor whose resistance value may be varied. Thus, a rheostat is a variable resistor.
It is used to change the resistance of circuits, and in this way to vary the value of current.
A rheostat consists of a coil and a switch. Take into consideration that wire used for the coil must have a very high resistance. When a rheostat is used its terminals are connected in series with the load. The switch is used to change the length of the wire through which the measured current passes. The resistance may be changed to any value from zero to maximum.
The longer the rheostat wire used in the circuit the greater the resistance.
Answer the questions:
1. What is this text about? 2. What type of resistor is a rheostat? 3. What is a rheostat used for? 4. In what way does a rheostat vary the value of current? 5. What elements does a rheostat consist of? 6. In what way are the termi - nals connected with the load? 7. What is the function of the switch?
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