Railway Science (Physics-Electric Current and its Effects) (Part-II)

In a series circuit, voltage varies across resistors while current remains the same, and a single component failure disrupts the entire circuit. In a parallel circuit, current varies across resistors while voltage remains the same, and component failure doesn't affect others.

Electromagnetic induction - When a coil is allowed to rotate in a uniform magnetic field, an induced current is produced in the coil. The angle between the motion of the conductor and the magnetic field determines the strength of the induced current. When the angle between the motion of the conductor and the magnetic field is 0°, the induced current produced is minimum. When the angle between the motion of the conductor and the magnetic field is 90°, the induced current produced is maximum.

Resistivity - A property that describes the extent to which a material opposes the flow of electric current through it. Materials that conduct electrical current easily have a low resistivity. Those that do not conduct electricity easily have a high resistivity. Compared to copper, silver has only slightly less resistivity and the resistivity of nichrome wire will be greater than copper wire.

Increased conductor length equals increased resistance in direct proportion. Resistance (R) is a measure of the opposition to current flow in an electrical circuit. SI unit: ohms (Ω). Conductors: The materials or substances that allow electricity to flow through them. Resistance of a conductor:

𝑅 = ρL/A  (R - resistance, ρ - resistivity constant, L - length of material, A - cross sectional area of material).

For wires of same length and thickness if the applied potential difference is same, then the wire with least resistivity will have the most current passing through it. Ohm’s law states that the voltage across a conductor is directly proportional to the current flowing through it, provided all physical conditions and temperatures remain constant. Ohm’s Law Equation: V = IR, where V is the voltage, I is the current and R is the resistance to the flow of current.

Materials that permit electricity to pass through. Example - silver, aluminum, and iron. Insulators - Materials that do not allow current to flow through. Example - plastic, wood and rubber. Resistance - Measure of the opposition to current flow in an electrical circuit, Unit - ohm (Ω).

When we place the thumb, the index finger and the middle finger mutually perpendicular to each other such that Thumb - Points towards the direction of force, Middle finger - Represents the direction of the current, and Index finger - Represents the direction of the magnetic field.

Fleming’s right-hand rule - Stretch the thumb, forefinger and middle finger of the right hand so that they are perpendicular to each other. If the forefinger indicates the direction of the magnetic field and the thumb shows the direction of motion of the conductor, then the middle finger will shows the direction of induced current.

A potential difference can be induced (created) in a conductor when there is movement between the conductor and a magnetic field. Electric Potential Difference - The amount of work done to carry a unit charge from one point to another in an electric circuit. When a magnet is moved with its south pole towards a closed coil, the nearer end of the coil acts according to Lenz’s law (the direction of the induced current will oppose the change in flux that created it. It's not a matter of increasing and decreasing, it's a matter of direction).

Electromagnet converts electrical energy into magnetic energy. An electromagnet seems to be a type of magnet that generates a magnetic field by using an electric current. Loudspeakers use an electric current flowing through a coil to generate a magnetic field.