# GATE (Graduate Aptitude Test in Engineering) Physics: Questions 79 - 82 of 659

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## Question 79

Appeared in Year: 2015

### Question

MCQ▾

A charge is distributed uniformly over a sphere, with a positive charge at its centre in . Also in , a charge is distributed uniformly over an ellipsoid with a positive charge at its centre. With respect to the origin of the coordinate system, which one of the following statements is correct?

### Choices

Choice (4)Response

a.

The dipole moment is non – zero in both figure (i) and figure (ii)

b.

The dipole moment is zero in both figure (i) and figure (ii)

c.

The dipole moment is zero in figure (i) but non – zero in figure (ii)

d.

The dipole moment is non – zero in figure (i) but zero in figure (ii)

## Question 80

Appeared in Year: 2014

### Write in Short

The intensity of a laser in free space is . The corresponding amplitude of the electric field of the laser is .

## Question 81

Appeared in Year: 2014

### Write in Short

If the vector potential

satisfies the Coulomb gauge, the value of the constant is ________.

## Question 82

Appeared in Year: 2015

### Write in Short

Let the Hamiltonian for two spin particles of equal masses , momenta and and position and be

where and denote the corresponding Pauli matrices, and . If the ground state has net spin zero, then the energy (in ) is ________.

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