Post

Magnetism and Capacitors

Electrician Trade Theory, Module-5

Posted Updated
Preview Image
By Roni
5 min read
Magnetism and Capacitors

⭕️ Show all Answers

Q1: Calculate the total capacitance value in the circuit.

Capacitor connected in series
  • 0.16 µF
  • 6 µF
  • 30 µF
  • 70 µF
Show Calculation \[ \text{For capacitors in series:}\]\[ \quad \frac{1}{C_T} = \frac{1}{C_1} + \frac{1}{C_2} + \frac{1}{C_3} \] \[ C_1 = 30\,\mu F,\quad C_2 = 10\,\mu F,\quad C_3 = 30\,\mu F \] \[ \frac{1}{C_T} = \frac{1}{30} + \frac{1}{10} + \frac{1}{30} = \frac{1 + 3 + 1}{30} = \frac{5}{30} \] \[ C_T = \frac{30}{5} = 6\,\mu F \]

Q2: What is the unit of capacitance?

  • Mho
  • Henry
  • Farad
  • Coulomb

Q3: What is the capacitance value of a capacitor that requires 0.5 coulomb to charge to 35 volt?

  • 0.014 F
  • 0.025 F
  • 0.14 F
  • 0.25 F
Show Calculation \[ C = \frac{Q}{V} = \frac{0.5}{35} = 0.014 \text{ F} \]

Q4: How the value of capacitance can be decreased?

  • Increasing the plate area
  • Increasing the resistance of the plates
  • Increasing the distance between the plates
  • Using high dielectric constant material

Q5: Which is the diamagnetic substance?

  • Air
  • Steel
  • Water
  • Platinum

Q6: Which factor affects the polarity of the electromagnet?

  • Length of the coil
  • Direction of current
  • Strength of current
  • Strength of the magnetic field

Q7: What is the unit of Magneto Motive Force (MMF)?

  • Ampere / M²
  • Ampere - M
  • Ampere - turns
  • Ampere / turns

Q8: What is the total inductance if 3 inductors \(L_1, L_2\) and \(L_3\) are connected in series?

  • \(L_T = L_1 × L_2 × L_3\)
  • \(L_T = L_1 + L_2 + L_3\)
  • \(L_T = \frac{1}{L_1} + \frac{1}{L_2} + \frac{1}{L_3}\)
  • \(L_T = \frac{1}{L_1 + L_2 + L_3}\)

Q9: What is the unit of permeance?

  • Ampere - turns
  • Weber/Ampere turns
  • Ampere turns/Weber
  • Weber/Square metre

Q10: Which rule is applied to find the direction of magnetic fields in a solenoid coil?

  • Cork screw rule
  • Right hand palm rule
  • Flemings left hand rule
  • Flemings right hand rule

Q11: Calculate the total value of capacitance of series capacitor circuit.

series capacitor circuit
  • 40µfd
  • 10µfd
  • 15µfd
  • 4µfd
Show Calculation \[ \text{For capacitors in series:}\]\[ \quad \frac{1}{C_T} = \frac{1}{C_1} + \frac{1}{C_2} + \frac{1}{C_3} \] \[ C_1 = 10\,\mu F,\quad C_2 = 10\,\mu F,\quad C_3 = 20\,\mu F \] \[ \frac{1}{C_T} = \frac{1}{10} + \frac{1}{10} + \frac{1}{20} = \frac{2}{10} + \frac{1}{20} \] \[ \frac{1}{C_T} = \frac{4}{20} + \frac{1}{20} = \frac{5}{20} \] \[ C_T = \frac{20}{5} = 4\,\mu F \]

Q12: What precaution to be taken before connecting the different voltage rating capacitors in series?

  • All the capacitors must be same manufacturer
  • Each capacitors voltage drop must be less than its voltage rating
  • Total capacitors value must be less than the lowest value of capacitor
  • Break down voltage of each capacitor must be same

Q13: Which material is the paramagnetic substance?

  • Cleat wiring
  • Copper
  • Bismuth
  • Graphite

Q14: What is the part marked as ‘X’ in B.H curve?

BH curve
  • Coercivity
  • Saturation point
  • Magnetizing force
  • Residual magnetism

Q15: What is the similar term in magnetic circuit for “conductance” in electrical circuit?

  • Reluctivity
  • Permeance
  • Reluctance
  • Permeability

Q16: What is the unit of Reluctance?

  • Weber / metre²
  • Weber / metre
  • Ampere turns / Weber
  • Ampere turns / metre²

Q17: Which is the correct expression of capacitance ‘C’ if the electric charge is ‘Q’ and the voltage is ‘V’?

  • \(C = \frac{Q}{V}\)
  • \(C = \frac{V}{Q}\)
  • \(C = V Q\)
  • \(C = \sqrt{VQ}\)

Q18: How can you increase the pulling strength of an electromagnet?

  • Increase the field intensity
  • Reduce the current in the coil
  • Reduce the number of turns in the coil
  • Increase the B-H curve of the material

Q19: Which defines the flux density is always lagging behind the magnetising force?

  • Hysteresis
  • Magnetic intensity
  • Magnetic induction
  • Residual magnetism

Q20: What is the effect on surrounding metal placed in a magnetic field?

  • Hysteresis
  • Skin effect
  • Eddy current
  • Dielectric stress

Q21: In which device the air capacitors are used?

  • TV tuner
  • Oscillator
  • Loudspeaker
  • Radio receiver

Q22: What will happen, if the polarized electrolytic capacitor is reversely connected?

  • No effect on the capacitor
  • Explode due to excessive heat
  • Current is reduced in the circuit
  • Value of capacitance will be increased

Q23: Which is the diamagnetic substance?

  • Wood
  • Nickel
  • Platinum
  • Manganese

Q24: What is the S.I unit of Flux density?

  • Tesla
  • Weber
  • Weber/metre
  • Ampere-turns

Q25: What indicates the shape of a BH curve (Hysteresis loop) of material?

  • Reluctance of the material
  • Field intensity of the substance
  • Magnetic properties of the material
  • Pulling power of the magnetic material

Q26: Which electrical quantity is directly proportional to the eddy current?

  • Voltage
  • Current
  • Frequency
  • Resistance

Q27: Which is the cause for changing the permeability?

  • Length
  • Flux density
  • Field intensity
  • Magneto motive force
Show Explanation
Increasing or decreasing field intensity (H) changes the alignment of magnetic domains, which affects the material’s permeability (μ). As permeability changes, it alters the resulting flux density (B). Therefore, field intensity is the cause, permeability is the response, and flux density reflects the magnetic effect inside the material.

Cause of changing permeability: Field intensity (H)
Effect of changing permeability: Change in flux density (B)

For more explanation visit this link https://g.co/gemini/share/d230ce7e109b

Q28: Which type of capacitor is used for space electronics?

  • Plastic film type
  • Ceramic disc type
  • Electrolytic-Aluminium type
  • Electrolytic-Tantalum type

Q29: What is the effect of the electrolytic capacitor, if open circuit fault occurs?

  • It will not function
  • It will burst at once
  • It will become leaky
  • It will function normally

Q30: What will be the change in value of capacitance if the distance of the plates are decreased in the capacitor?

  • Becomes zero
  • Remains same
  • Decreases
  • Increases

Q31: Which property of magnet is illustrated?

Magnet
  • Directive property
  • Induction property
  • Saturation property
  • Poles existing property

Q32: Which is a paramagnetic substance?

  • Air
  • Steel
  • Glass
  • Water

Q33: Which method of magnetization is used to make commercial purpose permanent magnets?

  • Induction method
  • Single touch method
  • Double touch method
  • Divided touch method

Q34: What is the effect of inductance if the distance between the turns increases?

  • Increases
  • Decreases
  • Becomes zero
  • Remains same

Q35: What is the function of dielectric insulator in capacitor?

  • Increases the strength of capacitance
  • Prevents any current flow between plates
  • Protects from short circuit between the plates
  • Helps to hold the charge in capacitor for long period

Q36: Which factor is determining the value of capacitance in capacitor?

  • Area of the plates
  • Shape of the plates
  • Material of the plates
  • Thickness of the plates

Q37: Which type of capacitors are used in RF coupling circuit?

  • Tantalum
  • Monolithic
  • Electrolytic
  • Metalized poly propylene
Found a mistake or mismatch in the question or answer? Let us know via email.
1st year, Trade Theory
Theory ITI
This post is licensed under CC BY 4.0 by the author.