Resistance 7b Flashcards
In what application might a change in resistance with temperature be desirable?
For the Total Air Temperature (TAT) probe used to measure the air temperature outside an aircraft.
What is a Positive Temperature Coefficient (PTC) Resistor?
A resistor whose resistance increases as the temperature rises.
What are the two types of thermistors based on their thermal characteristics?
Positive Temperature Coefficient (PTC) Resistors and Negative Temperature Coefficient (NTC) Resistors.
Can you name an application where a PTC thermistor might be used?
PTC thermistors might be used in safety devices to protect against overheating by increasing resistance and reducing current flow.
What is a Negative Temperature Coefficient (NTC) Resistor?
A resistor whose resistance decreases as the temperature rises.
What are the two common types of mechanically varied resistors?
The first type is used for making changes to the output of a circuit, like a rotary volume control. The second type is used for adjustments that do not need further changes in normal operation, often referred to as βtrimmersβ.
What types of materials can the resistive path in a variable resistor be made from?
The resistive path can be made from carbon composition, wire-wound, conductive plastic, or ceramic resistor.
Which type of resistive material is typically used for rheostats that carry a significant amount of current?
Wire-wound resistive paths.
How are the resistors arranged in a Wheatstone bridge?
There are two parallel branches; in the first branch, resistors R1 and R2 are connected in series, and in the second branch, resistors R3 and R4 are connected in series.
What is the primary function of a Wheatstone bridge?
It is used to compare the voltage in two branches of a circuit and can determine the value of an unknown resistance.
What component connects points a and b in a Wheatstone bridge?
Points a and b are connected via a galvanometer.
In a balanced Wheatstone bridge, what is the relationship between the resistors?
In a balanced Wheatstone bridge, the ratio of R1/R2 is equal to the ratio of R3/R4.
What happens to the galvanometer reading when the Wheatstone bridge is balanced?
When the Wheatstone bridge is balanced, the galvanometer shows zero or no current flow, indicating equal voltages at points a and b.
How can the unknown resistance in a Wheatstone bridge be calculated?
The unknown resistance can be calculated using the balanced bridge equation:
π
π₯=(π
2Γπ
3)/π
1, where
π
π₯ is the unknown resistor.
What practical applications use a Wheatstone bridge?
Wheatstone bridges are commonly used in strain gauge measurements, temperature sensors, and other precise resistance measurement applications.
