Potentiometers MCQ Quiz in मल्याळम - Objective Question with Answer for Potentiometers - സൗജന്യ PDF ഡൗൺലോഡ് ചെയ്യുക

Potentiometer:

• A DC potentiometer is the best means available for the measurement of DC voltage because it is based on the null balance technique and it is possible to measure DC voltage ranging in value from mV to hundreds of volts.
• The potentiometer measures voltage or potential difference by comparing an unknown voltage with a known voltage.
• A DC potentiometer can be used to measure the current, and resistance, and power.

Potentiometer is an instrument which is used to measure a unknown emf by comparison with known emf.

Sensitivity of potentiometer is the smallest potential difference can be measured using the potentiometer. It can be decreased by increasing its potential gradient. Thus, it can be decreased by following methods.

1) By decreasing length of the potentiometer wire as the length of the wire is directly proportional to resistance.

2) If the potentiometer wire is a fixed length, the potential gradient can be increased by increasing the current in the circuit by varying rheostat.

The correct answer is option 4)  3A

Calculation

The standard cell emf 2 volt is balanced at 50 cm

The voltage drop per unit length = 2/50 = 40 mV/cm

The voltage drop across a standard resistor of1 Ω is balanced at 75 cm

The voltage drop across 75 cm length = 40 × 10^-3 × 75 =  3V

The resistance of 75 cm length wire = 0.1 Ω

Current through the circuit = 3/ 1 = 3 A

• The Weston cell is a wet-chemical cell that produces a highly stable voltage suitable as a laboratory standard for calibration of voltmeters.
• The internal resistance of standard Weston cell is of the order of a fraction of an ohm.
• The open circuit EMF of the Weston standard cell used for standardization of potentiometer is 1.0183 V.

• D.C. potentiometer is used for accurate measurement of low D.C. voltage because the result obtained does not depend upon the actual deflection of a pointer
• A potentiometer is an instrument designed to measure an unknown voltage by comparing it with a known voltage
• Measurement using the comparison method is capable of a high degree of accuracy
• A potentiometer is extensively used for calibration of voltmeter and ammeters

The correct answer is 3 Only C.Key Points

• (A) Resistance is independent of temperature. This statement is incorrect. Resistance typically varies with temperature; for most conductors, resistance increases with an increase in temperature.
• (B) The more the voltage across a conductor, the more is the resistance. This statement is incorrect. According to Ohm's Law, V=IR" id="MathJax-Element-16-Frame" role="presentation" style="position: relative;" tabindex="0">V=IRV=IR" id="MathJax-Element-255-Frame" role="presentation" style="position: relative;" tabindex="0">V=IRV=IR" id="MathJax-Element-29-Frame" role="presentation" style="position: relative;" tabindex="0">V=IRV=IR" id="MathJax-Element-43-Frame" role="presentation" style="position: relative;" tabindex="0">V=IRV=IR" id="MathJax-Element-21-Frame" role="presentation" style="position: relative;" tabindex="0">V=IRV=IR" id="MathJax-Element-20-Frame" role="presentation" style="position: relative;" tabindex="0">V=IRV=IR V=IR V=IR V=IR V=IR V=IR $V = IR$ , where V" id="MathJax-Element-17-Frame" role="presentation" style="position: relative;" tabindex="0">VV" id="MathJax-Element-256-Frame" role="presentation" style="position: relative;" tabindex="0">VV" id="MathJax-Element-30-Frame" role="presentation" style="position: relative;" tabindex="0">VV" id="MathJax-Element-44-Frame" role="presentation" style="position: relative;" tabindex="0">VV" id="MathJax-Element-22-Frame" role="presentation" style="position: relative;" tabindex="0">V V V V V V $V$ is voltage, I" id="MathJax-Element-18-Frame" role="presentation" style="position: relative;" tabindex="0">II" id="MathJax-Element-257-Frame" role="presentation" style="position: relative;" tabindex="0">II" id="MathJax-Element-31-Frame" role="presentation" style="position: relative;" tabindex="0">II" id="MathJax-Element-45-Frame" role="presentation" style="position: relative;" tabindex="0">II" id="MathJax-Element-23-Frame" role="presentation" style="position: relative;" tabindex="0">I I I I I I $I$ is current, and R" id="MathJax-Element-19-Frame" role="presentation" style="position: relative;" tabindex="0">RR" id="MathJax-Element-258-Frame" role="presentation" style="position: relative;" tabindex="0">RR" id="MathJax-Element-32-Frame" role="presentation" style="position: relative;" tabindex="0">RR" id="MathJax-Element-46-Frame" role="presentation" style="position: relative;" tabindex="0">RR" id="MathJax-Element-24-Frame" role="presentation" style="position: relative;" tabindex="0">R R R R R R $R$ is resistance. This implies that voltage is directly proportional to the product of current and resistance, but it does not mean that resistance changes with voltage. Resistance is a property of the material and geometry of the conductor.
• (C) The S.I unit of resistance is ohm. This statement is correct. The standard unit of resistance in the International System of Units (SI) is the ohm, symbolized by the Greek letter omega (Ω).

The basic working principle of this is based on the fact that the fall of the potential across any portion of the wire is directly proportional to the length of the wire, provided wire has uniform cross-sectional area and the constant current flowing through it.

CONCEPT:

• A potentiometer is a device mainly used to measure emf of a given cell and to compare emf’s of cells.
• It is also used to measure the internal resistance of a given cell.
• If Potential across AJ (V) is equal to emf E’ then no current will flow in the galvanometer circuit this condition to known as null deflection position, length AJ (x) is known as balancing length.

In balanced condition E’ = VAJ

\(E' = \frac{{E\;{R_{AB}}}}{{\left( {r + {R_{AB}}} \right) \times AB}}x\)

EXPLANATION:

Working current of potentiometer

\({I_w} = \frac{{3.2}}{{200 + 200 + 2800}} = 1\;mA\)

Voltage drop across sliding wire = 1 mA × 200 = 200 mV

Now, 

As the potentiometer works on the null balance technique, the current through the galvanometer should be zero.

⇒ E = voltage drop across sliding wire = 200 mV

A hydrometer is used to measure the density of a liquid, in this case, the electrolyte solution in a battery cell. The density of the electrolyte is directly related to its concentration of sulfuric acid and, consequently, to the state of charge of the cell. A fully charged cell will have a higher specific gravity than a discharged cell.

• Current is the flow of electricity, and a hydrometer does not measure this directly.
• Power is the rate at which energy is transferred, and a hydrometer does not measure this either.
• Voltage is the potential difference between two points, and while it is related to the state of charge of a cell, it is not directly measured by a hydrometer.
• Therefore, the specific gravity is the only option that is directly measured by a hydrometer and is related to the state of charge of a cell.

Potentiometer :

• A three terminal device which is used to vary resistance.
• It has sliding contact through which by moving or rotating resistance is varied. 
• It acts as voltage divider circuit.
• Potentiometer is variable resistor or rheostat.

Additional InformationPotentiometer is used to find voltage or EMF at a particular position due to its voltage dividing capacity.

Potentiometer:

It is an instrument designed to measure an unknown voltage by comparing it with a known voltage or standard voltage. It is also used for comparing the emf of two cells.

Characteristics of potentiometer:

• As it measures the unknown voltage by comparing it with standard voltage rather than by actual deflection of the pointer. This ensures a high degree of accuracy.
• The potentiometer measures the unknown voltage using null or balance conditions, hence no power is required for the measurement.
• The determination of voltage using a potentiometer is quite independent of the source resistance.

The Basic potentiometer circuit is shown below,