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प्रश्न
Justify your answers for each case.
State the significance of the negative value of electrostatic potential energy of a system of charges.
Three charges are placed at the corners of an equilateral triangle ABC of side 2.0 m as shown in the figure. Calculate the electric potential energy of the system of three charges.
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उत्तर
U = `(KQ_AQ_B)/r + (KQ_BQ_C)/r + (KQ_CQ_A)/r`
U = `K/r[Q_AQ_B + Q_BQ_C + Q_CQ_A]`
U = `K/r xx [4 xx 10^-6 xx -4 xx 10^-6] + [-4 xx 10^-6 xx 2 xx 10^-6] + [2 xx 10^-6 xx 4 xx 10^-6]`
U = `K/r xx 10^-12[-16 - 8 + 8]`
U = `K/r xx 10^-12(-16)`
U = `(-9 xx 10^9 xx 10^-12 xx 16)/2`
U = -72 × 10-3 J
U = -7.2 × 10-2 J
A negative value signifies a stable system.
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संबंधित प्रश्न
The work done in bringing a unit positive charge from infinite distance to a point at distance x from a positive charge Q is W. Then the potential at that point is ______.
- Assertion (A): An electron has a high potential energy when it is at a location associated with a more negative value of potential, and a low potential energy when at a location associated with a more positive potential.
- Reason (R): Electrons move from a region of higher potential to region of lower potential.
Select the most appropriate answer from the options given below:
In the circuit shown in figure initially, key K1 is closed and key K2 is open. Then K1 is opened and K2 is closed (order is important). [Take Q1′ and Q2′ as charges on C1 and C2 and V1 and V2 as voltage respectively.]
Then
- charge on C1 gets redistributed such that V1 = V2
- charge on C1 gets redistributed such that Q1′ = Q2′
- charge on C1 gets redistributed such that C1V1 + C2V2 = C1E
- charge on C1 gets redistributed such that Q1′ + Q2′ = Q
- In a quark model of elementary particles, a neutron is made of one up quarks [charge (2/3) e] and two down quarks [charges –(1/3) e]. Assume that they have a triangle configuration with side length of the order of 10–15 m. Calculate electrostatic potential energy of neutron and compare it with its mass 939 MeV.
- Repeat above exercise for a proton which is made of two up and one down quark.
The symbol, SI unit, and nature of electrostatic potential energy are respectively:
For a system of unlike charges (attractive force), an external agent must do work to separate them because the system:
While assembling a system of charges, the work done in bringing the first charge \[q_1\] from infinity to its Position 1 is:
The total electrostatic potential energy of a three-charge system is:
For two like charges (both positive or both negative), the sign of \[(q_1 q_2)\] and the resulting sign of the potential energy U are:
For a pair of like charges, the positive potential energy (U > 0) physically signifies that:
