Physics: CUET Mock Test - 9 - CUET MCQ

A wire-wound resistor is an electrical passive component that limits current. wire-wound resistors are made by winding the wires of an alloy like manganin on an insulating base. They are relatively insensitive to temperature.

CONCEPT:

• Electromagnetic Spectrum is the orderly distribution of electromagnetic waves in accordance with their wavelength(λ) or frequency(ν) into a group of waves having widely differing properties. There are no sharply defined boundaries and these different waves do overlap each other.
• The table below represents the frequency range and application of various electromagnetic waves

EXPLANATION:

• The spectrum represents the arrangement in the order of frequency and wavelength.
• The decreasing order of wavelengths is opposite to the increase in frequency.
• The wavelength and frequency of waves are inversely related.

-------(1)

Then the waves can be arranged as

According to relationship 1, Equation 2 can be rewritten as

• Hence Option 2 is the answer

CONCEPT:

The De Broglie wavelength of the electron is written as;

°A

here, is the wavelength in °A and V in Volt is the potential difference.

CALCULATION:

Given,

The wavelength of the electron is 1.227 × 10−2 nm

1.227 × 10−2 nm = 1.227 × 10−11 m

1.227 × 10−11 m = 1.227 × 10−11 × 1010 °A

1.227 × 10−2 nm = 12.27 × 10−2 °A

Using equation (1) we have;

°A

⇒

⇒ ​

⇒ V = 10⁴ volts

Hence, option 2) is the correct answer.

The correct answer is rate of change in magnetic flux.Key Points

• Induced EMF in a coil during the phenomenon of electromagnetic induction is directly proportional to the rate of change in magnetic flux.
• Electromagnetic induction is the process of generating an electromotive force (EMF) in a conductor by changing the magnetic field around it.
• The magnitude of the induced EMF depends on the rate of change of magnetic flux through the coil.
• This means that the faster the magnetic field changes, the greater the induced EMF will be.

Additional Information

• Magnetic flux is the amount of magnetic field passing through a surface.
  • It is given by the product of the magnetic field strength and the area of the surface perpendicular to the field.
  • However, the induced EMF is directly proportional to the rate of change of magnetic flux, not the magnetic flux itself.
• Resistance of the circuit does not affect the magnitude of induced EMF.
  • It only affects the current flowing through the circuit according to Ohm's Law.
• The phenomenon of electromagnetic induction was discovered by Michael Faraday in 1831.
• Faraday's Law of Electromagnetic Induction states that the EMF induced in a circuit is proportional to the rate of change of magnetic flux through it.
• The direction of induced EMF is given by Lenz's Law, which states that the direction of the induced EMF is such that it opposes the change in magnetic flux that produced it.

Zener Diode is mostly used as Voltage Regulator.

CONCEPT:

Zener diode: A Semiconductor Diode blocks current in the reverse direction, but will suffer from premature breakdown or damage if the reverse voltage applied across becomes too high.

Zener diode as voltage regulator: The Zener diode is connected with its cathode terminal connected to the positive rail of the DC supply so it is reverse biased and will be operating in its breakdown condition. Resistor Rs is selected so to limit the maximum current flowing in the circuit.

EXPLANATION:

• A Zener diode is used as a voltage regulator in reverse biased mode.
• The breakdown voltage in the Zener diode when connected in the reverse-biased is called Zener voltage. This Zener voltage so steady and constant, it has huge applications in circuits, most importantly, voltage regulation.

So option 4 is correct.

Van de Graff generator is used to create a large amount of static electricity. A Van de Graff generator uses static electricity and a moving belt to charge a large metal sphere to a very high voltage. As the belt moves, electrons move from the rubber belt to the silicon roller, causing the belt to become positively charged and the roller to become negatively charged. As a result, it builds up positive charge.

A Van de Graff generator, by means of a moving belt and suitable brushes, transfers charge continuously to a large spherical conducting shell. As a result, a potential difference of the order of several million volts is built up and this can be used for accelerating charged particles.

A Van de Graaff generator is an electrostatic device that accumulates charge on a large metal sphere, creating a high potential difference (voltage) relative to the ground. It is primarily used to generate high voltages for experiments, such as accelerating charged particles or demonstrating electrostatic phenomena.

• A: Incorrect, as it produces low current, not large current.
• B: Incorrect, as it is not used for resistance measurement.
• C: Incorrect, as it produces direct current, not alternating current.

A Van de Graff generators produces large voltage and less current. A Van de Graff generator is an electrostatic generator which creates very high electric potentials. It produces very high voltage direct current electricity at low current levels.

For a half-wave rectifier,

r =1.21

Power P= V²/R​
If length reduced 10% then new resistance of filament will be R′.
R′=R−10% of R
R′=0.9R
Now new power of heater is P2​
P_2​= V²​​/R′ = V²/0.9R​​=1.1P
% increase power=11%

• Both potentiometer and voltmeter are devices to measure potential difference.
• EMF is the terminal p.d between the electrodes of a cell in open circuit, i.e., when no current is drawn from it.
• Potentiometer measures the potential difference using null deflection method, where no current is drawn from the cell; whereas voltmeter needs a small current to show deflection.
• So, accurate measurement of p.d is done using a potentiometer.

• Copper is a conductor and we know that for conductors, resistance is directly proportional to temperature. Therefore on decreasing temperature resistance also decreases.
• Whereas, germanium is a semiconductor and for semiconductors, resistance is inversely proportional to temperature.
• So on decreasing temperature resistance increases.

Ammeter is a device used to measure current. Since it has to allow the complete current flowing in the circuit through it, it has to be connected in series. For this reason, ammeters have very low values of resistances so that they do not add to the value of resistance connected in the circuit.

Kirchhoff's second law, also known as the Kirchhoff's voltage law (KVL) states that the sum of all voltages around a closed loop in any circuit must be equal to zero. This again is a consequence of conservation of energy.

The balance point will not change . For balancing of wheatstone bridge four arms of resistors are responsible. Interchange the position of galvanometer and cell does not affect balancing of wheatstone bridge.

Resistance in a conductor is defined by Ohm’s Law, which states:

• V (Voltage) = I (Current) × R (Resistance)
• R = V/I

This means that resistance is the ratio of voltage across a conductor to the current flowing through it. A higher resistance indicates that more voltage is needed to achieve the same current.

Thus, intensive recombinations of electrons and positive ions into neutral atoms and molecules occur. This results in the emission of light by the discharge, i.e., the negative glow is mainly due to a glow of recombination. Hence in electric discharge the electric current is due to both electrons and positive ions.

Current density is equal to Electric current divided by a given surface area, or it is the current flowing per a given cross section area.
The current density decreases with increase in cross section area which means they are inversely proportional.

The resistivity of a semiconductor decreases with temperature. This is because of increasing temperature, the electrons in the valence band gain sufficient thermal energies to jump to the conduction band. As the number of electrons in the conduction band increases, so conductivity increases and resistivity decreases.

Let  n₁​ and n₂​ be the densities of charge carriers in the two wires, Vd₁​​ and Vd₂​​ be the drift velocities of charge carriers in the two wires,
A be the area of cross section,
e is the charge on electron and
I is the current flowing through both the wires
Hence, I=n₁​eAV_d1​​=n_1​eAV_d2​​
∴n₁​V_d1​​=n₂​V_d2​​
∴ V_d1/V_d2​​ ​​​=​n2​​/n1
∴ ​​V_d1​​​/ V_d2=4/1​

In case of semiconductor Resistivity∝1​/temperature
In this case as temperature increases electrons jump to conduction band resistance decreases R ∝ ρ(Resistivity) so resistivity also decreases and current increases.
Vibration of electrons increases with rise in temperature and hence collision between ions and electrons increases with temperature.

Given A storage battery is connected to a charger for charging with a voltage of 12.5 Volts. The internal resistance of the storage battery is 1 ohm. When the
charging current is 0.5 A, the emf of the storage battery is:
When the battery is charging
We know that
V = e + i r  
V = 12.5, i = 0.5, r = 1  
12.5 = e + 0.5 x 1
12.5 = e + 0.5
e = 12.5 – 0.5
e = 12 v

Here, R_G = 70Ω, r_s = 0.03Ω
∴ R = 
= 0.02998 
= 0.03Ω

Galvanometer is a very sensitive instrument, therefore it can not measure high potential difference.
In order to convert a Galvanometer into voltmeter, a very high resistance known as "series resistance" is connected in series with the galvanometer.

Given N = 35,
r = 25cm
= 25 × 10⁻²m
I = 11A
Then magnetic moment associated with this circular coil
M = NIA = NIπr² = 35 × 11 × 3.14 × (25 × 10⁻²)²
= 75.56 A m²

Here, M = 0.65JT⁻¹,
d = 8cm
= 0.08m
The field produced by magnet at axial point is given by
B = 
= 2.5 × 10⁻⁴T along SN

The magentic moment is given by
m = NIA = NIπr²
= 100 x 3.2 x 3.14 x (10 x 10^-2)²
= 100 x 3.2 x 3.14 x 10^-2
= 10 A m²

The torque depends upon n, I, A, B and θ. But it does not depend upon the shape of the loop (rectangular, circular, triangular, etc.)