Hole is :
`a)` An anti-particle of electron
`b)` A vacancy created when an electron leaves a covalent bond
`c)` Absence of free electrons
`d )` An artificially created particle

Which atom can have more than eight valence electrons when it is forming covalent bonds ?

Which atom can have more than eight valence electrons when it is forming covalent bonds ?

How can a nucleus lose electrons ( beta -particles) even though free electrons are not present in it?

An electron moves in a uniform magnetic field and follows a spiral path as shown in Fig. 1.30. State the following statements as True or False. a. Angular velocity of the electron remains constant. b. Magnitude of velocity of the electron decreases continuously. c. Net force on the particle is always perpendicular to its direction of motion. d. Magnitude of net force on the electron decreases continuously.

Assertion:The mass of beta -particles when they are emitted is higher than the mass of electrons obtained by other means. Reason: beta -particle and electron , both are similar particles.

When alpha particle captures and electron, then it becomes a

True or False: When an atom loses or gains electrons, it becomes a charged particle.

Alpha particle would go undiviated when it collides with an electron of gold foil . Why ?

The positron is a fundamental particle with the same mass as that of the electron and with a charge equal to that of an electron but of opposite sign. When a positron and an electron collide, they may annihilate each other. The energy corresponding to their mass appears in two photons of equal energy. Find the wavelength of the radiation emitted. [Take : mass of electron = (0.5//c^(2))MeV and hc = 1.2 xx 10^(-12) MeV-m , where h is the Planck's constant and c is the velocity of light in air.

A currrent I is passed through a silver strip of width d and area of cross section A. The number of free electrons per unit volume is n. (a) Find the drift velocity v of the electrons. (b) If a magnetic field B exists in the region as shown in what is the average magnetic force on the free electrons? (c) Due to the magnetic force, the free electrons get accumulated on one side of the conductor along its length. This produces a transverse electric field in the conductor which opposes the magnetic force on the electrons. Find the magnitude of the electric field which will be the potential diference developed across the width of the conductor due to the electron- accumulation? The appearance of a transverse emf, when a current-carrying wire is placed in a magnetic field, is called hall effect.