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The unit for the quantity of electricity is the coulomb.

1 coulomb is defined as the quantity of electricity transported in one second by a current of one ampere.

The attraction capacity of an electromagnet increases when the flux density increases because a higher flux density means a stronger magnetic field is produced in the core and surrounding region. This stronger field results in a greater force of attraction on nearby ferromagnetic materials, making flux density a key factor in determining the strength of an electromagnet.

The relative permeability of ferromagnetic materials is not constant because it changes significantly with the applied magnetic field, temperature, and magnetic history of the material (hysteresis). As the field increases, domains align in a non-linear way, causing permeability to vary widely rather than remain fixed. This behavior is what makes ferromagnetic materials different from diamagnetic and paramagnetic materials, where permeability is nearly constant.

The uniform magnetic field is the field in which all lines of magnetic flux are parallel and equidistant.

Uniform magnetic fields have the same strength and direction at every point in the field. This means that the magnetic field lines are evenly spaced and parallel to each other. It's a characteristic feature of some specific arrangements of magnets or coils, where the magnetic field lines are consistent and regular.

So, the correct option is:

• the field in which all lines of magnetic flux are parallel and equidistant

A keeper is used to provide a closed path for magnetic flux because it bridges the poles of a magnet with a ferromagnetic material, allowing the magnetic field lines to complete their loop through a low-reluctance path. This helps preserve the magnet’s strength by preventing the loss of flux into the surrounding air and maintaining a stable magnetic circuit.

When a magnet is in motion relative to a coil, the induced electromotive force (e.m.f.) does not depend upon the resistance of the coil.

The induced e.m.f. is determined by Faraday's law of electromagnetic induction, which states that the magnitude of the induced e.m.f. is proportional to the rate of change of magnetic flux through the coil.

This rate of change of magnetic flux is influenced by factors such as the speed of motion of the magnet, the strength of the magnetic field, and the number of turns of the coil.

However, the resistance of the coil affects the current that flows due to the induced e.m.f. Once induced, the current in the coil will be influenced by the resistance according to Ohm's law (V = IR), where V is the voltage (induced e.m.f.), I is the current, and R is the resistance. But the induced e.m.f. itself is not directly dependent on the resistance of the coil.

So, the correct answer is resistance of the coil.

Among the options provided, Tesla is not a unit of flux.

• Maxwell: The Maxwell (Mx) is a unit of magnetic flux, named after James Clerk Maxwell, and it is equivalent to one line of magnetic flux.

• Tesla: The Tesla (T) is a unit of magnetic flux density or magnetic induction, not of flux itself. It measures the strength of the magnetic field.

• Weber: The Weber (Wb) is the SI unit of magnetic flux. One Weber is equal to one Tesla multiplied by one square meter (T⋅m²), representing the total magnetic field passing through a surface.

So, the correct answer is Tesla.

The magnetization and applied magnetic field in ferromagnetic materials are related non-linearly because their response is affected by domain alignment and hysteresis effects. As the external magnetic field increases, the magnetic domains gradually align, but not in a proportional or reversible way, causing the magnetization to change in a curved, path-dependent manner. This results in a hysteresis loop, confirming the non-linear relationship between magnetization and the applied field.

The correct statement is that the magnetic flux inside the exciting coil is the same as on its outside surface (in the ideal case). This follows from Gauss’s law for magnetism, which implies that magnetic field lines form continuous closed loops with no beginning or end, so the flux entering a region must equal the flux leaving it. As a result, the magnetic flux inside the coil is equal to the flux on its outside surface when leakage is neglected.

Ferromagnetic substances have positive susceptibility. Magnetic susceptibility indicates whether a material is attracted or repelled by a magnetic field. Ferromagnetic materials, such as iron, cobalt, nickel, and some rare earths, have a large positive susceptibility. In the absence of external fields, ferromagnetic materials have a magnetic moment and exhibit strong, permanent magnetization.