Capacitance

1. Name the physical quantity whose SI unit is Coulomb/volt.

• Electric Field

• Charge

• Electric Potential

• capacitance

Answer explanation

The SI unit Coulomb/volt is equivalent to farad, which is the unit of capacitance. Capacitance measures a capacitor's ability to store charge per unit voltage, making it the correct answer.

2. 12pF capacitor is connected to 50V battery , How Much electrostatics energy is stored in the capacitor

• 1.5x10-8J

• 1.5x10-9J

• 1.5x10-10J

• 1.5x10-11J

• Option 5

Answer explanation

The energy stored in a capacitor is given by the formula U = 1/2 C V^2. Here, C = 12pF = 12 x 10^-12 F and V = 50V. Thus, U = 1/2 * 12 x 10^-12 * (50)^2 = 1.5 x 10^-8 J. Therefore, the correct answer is 1.5x10-8J.

11. 64 identical drops each of capacity 5µF combine to form a big drop , what is the capacity of big drop

• 11µF

• 20µF

• 10µF

• 163µF

Answer explanation

When 64 identical drops of 5µF combine, they act like capacitors in parallel. The total capacitance is the sum: 64 * 5µF = 320µF. However, if they combine to form a single drop, the effective capacitance is 20µF.

12. If the potential of capacitor having capacity 6µF is increased from 10V to 20V, then increases in its energy will be

• 4x10-4 J

• 7x10-4 J

• 9x10-4 J

• 14x10-4 J

Answer explanation

The energy stored in a capacitor is given by U = 1/2 C V^2. For 10V, U1 = 1/2 * 6µF * (10V)^2 = 0.0003 J. For 20V, U2 = 1/2 * 6µF * (20V)^2 = 0.0006 J. The increase in energy is U2 - U1 = 0.0006 J - 0.0003 J = 9x10-4 J.

14. Capacitor stores which type of energy?

• kinetic energy

• vibrational energy

• potential energy

• heat energy

Answer explanation

A capacitor stores energy in the form of an electric field, which is a type of potential energy. This energy can be released when the capacitor discharges, making 'potential energy' the correct answer.

A Capacitor

• provide a specific value of capacitance

• stores energy in a electrostatic field 

• opposes any change in voltage

• all of the above

Answer explanation

A capacitor provides a specific value of capacitance, stores energy in an electrostatic field, and opposes any change in voltage. Therefore, the correct answer is 'all of the above'.

Tags

NGSS.HS-PS2-4

NGSS.HS-PS3-2

The capacitance of a parallel-plate capacitor can be increased by: 

• increasing the charge 

• decreasing the charge 

• increasing the plate separation

• decreasing the plate separation 

Answer explanation

The capacitance of a parallel-plate capacitor is given by C = ε(A/d), where A is the area and d is the plate separation. Decreasing the plate separation (d) increases capacitance (C), making it the correct choice.

1CV^-1 is expressed as one ____.

• volt

• ohm

• farad

Answer explanation

1 CV⁻¹ is the unit of capacitance, which is defined as one farad. Therefore, 1 CV⁻¹ is expressed as one farad.

The energy of a charged capacitor is given by the expression (q= charge on the conductor and C = its capaciance)

Answer explanation

The energy stored in a capacitor is given by the formula \( \frac{q^2}{2C} \). This formula shows that the energy is proportional to the square of the charge and inversely proportional to the capacitance, making \( \frac{q^2}{2C} \) the correct choice.

A capacitor of capacitance 30μF is fully charged from a 10 V d.c. supply. Calculate the charged stored by the capacitor

• 3.0 mC

• 0.30 mC

• 300 mC

• 330 kC

Answer explanation

The charge (Q) stored in a capacitor is calculated using the formula Q = C × V. Here, C = 30μF = 30 × 10^-6 F and V = 10 V. Thus, Q = 30 × 10^-6 F × 10 V = 0.30 mC. Therefore, the correct answer is 0.30 mC.