###### Asked by Andy Blackwell in Uncategorized

Uncategorized

# What is a typical dc resistance for a crt deflection coil. does 0.2 ohms seem reasonable?

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## Related Questions

###### Asked in Electronics Engineering, Electrical Engineering

### Why shunt resistance used in ammeter and why is it connected in parallel?

An ammeter's coil requires very little current for full-scale
deflection (fsd). So, to measure a current above its fsd value,
most of that current must be allowed to bypass the coil. This is
achieved by placing a very low value shunt resistance in parallel
with the coil ('shunt' is an archaic word for 'parallel').

###### Asked in Physics

### What is weston galvanometer?

###### Asked in Home Electricity, Electronics Engineering, Electrical Engineering

### Why is there a difference in current in a coil when you apply dc voltage and then AC voltage to it?

A coil has both resistance and inductance. When you apply a d.c.
voltage, the opposition to current is the resistance of the coil.
When you apply an a.c. voltage, the opposition to current is
impedance -the vector-sum of the coil's resistance and its
inductive reactance. Inductive reactance is proportional to the
inductance of the coil and the frequency of the supply.

###### Asked in Physics, Electronics Engineering

### What is deflection sensitivity of a cathode-ray oscilloscope?

There is basically two cases:
(It is recommended to read about Cathode Ray Tube Deflection
prior to read this)
1 - Electrostatic Deflection:
Is the voltage necessary to move the electronic beam by a unit
of lenght. Usually is V/cm or V/in.
Since there is no significant current flowing on the deflection
plates, and these kind of CRTs (Cathode Ray Tubes) are using on
measuring devices (on wich the lenght of the trace on the screen
will be measured in a way or another), only the voltage is
relevant
on the specification of the CRT, and its effect on the moving of
the bean.
CRT manufacturers made a tremendous effort to make the
relationship between the Voltage on the plates and the beam
deflection to be linear.
2 - Magnetic Deflection:
Used on most popular CRTs, as TVs, Monitors (now being replaced
by LCDs).
Is the product of the square of the total (Ap-p)current needed
to deflect the beam tottaly on the screen (from left to right -
horizontal deflection, or top to bottom - vertical deflection), and
the inductance of the coil.
It is understood as the minimum energy that the inductor (the
deflection coil) must store to generate the magnetic field and move
the beam totally on the screen.
Magnetic is the most complicated deflection since there are
several factor affecting the performance of the circuit, i.e. coil
resistance, geometric limitations, core saturation, variation of
core permeability.
Is the product of the inductance of the coil by the peak-to-peak
current, squared.
Most of the time is given in mHApp^2, but less often found in
OhmsApp^2
Needless to say that the CRT using this kind of deflection uses
several types of correction of linearity, because now the beam does
no move in a linear way with the surface of the screen. The most
popular are East-West correction, Pin-Cushion correction, and
S-correction. There is basically two cases:
(It is recommended to read about Cathode Ray Tube Deflection
prior to read this)
1 - Electrostatic Deflection:
Is the voltage necessary to move the electronic beam by a unit
of lenght. Usually is V/cm or V/in.
Since there is no significant current flowing on the deflection
plates, and these kind of CRTs (Cathode Ray Tubes) are using on
measuring devices (on wich the lenght of the trace on the screen
will be measured in a way or another), only the voltage is
relevant
on the specification of the CRT, and its effect on the moving of
the bean.
CRT manufacturers made a tremendous effort to make the
relationship between the Voltage on the plates and the beam
deflection to be linear.
2 - Magnetic Deflection:
Used on most popular CRTs, as TVs Monitors (now being replaced
by LCDs).
Is the product of the square of the total (Ap-p)current needed
to deflect the beam tottaly on the screen (from left to right -
horizontal deflection, or top to bottom - vertical deflection), and
the inductance of the coil.
It is understood as the minimum energy that the inductor (the
deflection coil) must store to generate the magnetic field and move
the beam totally on the screen.
Magnetic is the most complicated deflection since there are
several factor affecting the performance of the circuit, i.e. coil
resistance, geometric limitations, core saturation, variation of
core permeability.
Is the product of the inductance of the coil by the peak-to-peak
current, squared.
Most of the time is given in mHApp^2, but less often found in
OhmsApp^2
Needless to say that the CRT using this kind of deflection uses
several types of correction of linearity, because now the beam does
no move in a linear way with the surface of the screen.

###### Asked in Physics

### What would happen if the current passing through the coil was too large?

The coil offers some amount of Resistance to the flow of
Electric current through the coil. The Resistance of the coil
depends on the material used to make the coil and the thickness of
the coil wire ( its gauge ) When a current flows through the coil,
the voltage drop across the coil and the Power dissipated in the
coil both are proportional to the magnitude of current and the coil
resistance. Normally the coil is rated to carry certain current and
dissipate certain amount of power without causing any damage. If a
large magnitude of current flows through the coil beyond its rating
, the voltage drop across the coil and the power dissipation in the
coil both increase substantially causing over heating of the coil.
This can damage the coil and may result in burning of the coil

###### Asked in Electronics Engineering, Electrical Engineering

### What is the purpose of the series resistor in your designed ammeter circuit?

You appear to be referring to a 'swamping resistor' which
is connected in series with a moving-coil ammeter's moving
coil.
To minimise any errors due to temperature changes in the
resistance of the instrument's moving coil, the coil is connected
in series with what is termed a 'swamping resistor' whose
resistance is large in comparison with that of the moving coil, and
which is manufactured from an alloy with a very low
temperature coefficient of resistance (i.e. a metal whose
resistance is hardly effected by wide variations in
temperature).
For example, if the resistance of a 1-Ω moving coil increases
to, say, 1.1 Ω, when its rated current flows through it, this will
introduce a 10% error in the instrument's reading.
But by calibrating the instrument with a series swamp resistor
of, say, 49 Ω, the overall resistance at rated current will become
50.1 Ω. This will result in an error of just 0.2%.
A swamping resistor, then, is an integral part of all
moving-coil instruments and, when we refer to an instrument's 'coil
resistance', we actually mean the combined resistance of the
moving coil itself and its swamping resistor.

###### Asked in Electronics Engineering, Electrical Engineering

### Why in coil power factor is low?

A coil of wire acts as an inductor; it will have a very small
resistance, and a relatively large inductance. Power factor is
effectively the resistance divided by the impedance (made up of
resistance and inductance), so the larger the inductance relative
to the resistance, the lower the power factor will be.

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