Question

- A strain gauge with a gauge factor of 3.3 consists of a 50cm wire with a 20µm diameter and a 300Ω resistance . When complete length of the wire is strained positively the resistance change is measured as 0.6 Ω . Calculate the change in wire length and diameter

Answer #1

A strain gauge is used to measure the tension force in a
0.75-in. diameter bar of steel. The strain gauge has a nominal
resistance of 180 ? and a GF of 4. The strain gauge is connected to
a bridge (which is supplied with 10 Vdc). The bridge was initially
balanced. After the bar is put under tension, the bridge output
voltage goes to 0.0006 Vdc. Draw a schematic of the setup and
calculate the force on the bar.

Derive a resistive deflection bridge suitable for strain
measurement using the strain gauge with factor G=2.0, Unrestrained
resistance R0=120 Ohm and temperature sensitive to the ambient
temperature. The current through the sensor must not exceed 1 mA.
Motivate your design choices clearly. Plot the output voltage of
the deflection bridge for various choices of the component values
in the bridge, illustrating the effect of your design choices.

By what factor does the resistance of a copper wire change if
its length quadruples and its diameter quadruples? (If the
resistance doubles, enter "2"; if it decreases by a factor of
three, enter "1/3", etc.)

Even when using three-wire connections to a strain gage to
reduce the effects of leadwire resistance changes with temperature,
a phenomenon called leadwire desensitization can occur. If the
magnitude of the leadwire resistance exceeds 0.1% of the nominal
gage resistance, significant error can result. Assuming a 22-gauge
(AWG)† copper leadwire (resistivity 1.68·10-8
Ωm) and a standard 120 Ω gage, how long can the (individual) leads
(in inches) be before there is leadwire desensitization?

By what factor does the resistance of a copper wire change if
its length quadruples and its diameter quadruples? (If the
resistance doubles, enter "2"; if it decreases by a factor of
three, enter "1/3", etc.)
(4/9 is not correct)

In the American Wire Gauge (AWG) system, a 16-gauge wire has a
diameter of 0.0500 inches. A copper wire of this size is only rated
to withstand a current of 15 amps. Design an electromagnet that has
a magnetic field of 0.18 T at the center.
a) What is the ratio of the number of turns to the radius of the
magnet you designed? (Hint: Do this first!)
b) How many turns does your electromagnet have? What is the
radius...

A physics technician makes a circular coil consists of 120 turns
of copper wire with a resistance of 0.6 Ω. The coil radius is 6 cm.
the coil is connected to a 12 V battery. (a) Calculate the magnetic
moment of the coil. (b) If the coil was placed between the pole
faces of a magnet where the magnetic field strength was 0.5 T,
calculate the maximum torque on the coil.

PLEASE SHOW ALL WORK!
00-gauge copper wire has a diameter of 9.266 mm and a
resistivity of 1.68 × 10−8 Ω · m at 20.0◦C. The wire is 1.00m in
length.
a) What is the power loss in the wire if the wire carries 110.
A?
b) The temperature coefficient of resistivity for copper is α =
3.90 × 10−3 ◦C−1. If the copper is at 40.0◦C, what is its new
resistivity?
c) If it still has the same power...

00-gauge copper wire has a diameter of 9.00 mm. Calculate the
power loss in 1.25 kilometer of such wire when it carries a current
90 A?

A length of copper wire carries a current of 14 A, uniformly
distributed through its cross section. Calculate the energy density
of (a) the magnetic field and (b)
the electric field at the surface of the wire. The wire diameter is
2.6 mm, and its resistance per unit length is 2.7 Ω/km.

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