Capacitance, Resistance and Electromagnetism

• Zeal Education Society's Zeal Polytechnic is in Pune, India.
• This is for the first year of a diploma in Electrical Engineering.
• The scheme is I, and it is semester II.
• The subject covered is Fundamentals of Electrical Engineering, with the subject code 22212.
• MSBTE question papers and model answers are included.

Direct Current vs. Alternating Current

• Direct current's magnitude and direction do not change over time. Conversely, alternating current has both magnitude and direction that continuously change over time.
• Direct current is not possible to use a transformer on whereas alternating current is possible.
• Direct current circuits are more complicated in design and alternating current circuits are simpler.
• Direct current frequency is zero, where alternating current is either 50 Hz or 60 Hz, depending on the country.
• Direct current is obtained from a battery, cell, or DC generator; alternating current is from an alternator.
• Direct current applications include DC machines, HVDC systems and electroplating
• Alternating current applications include AC machines as well as domestic and industrial supply

Electrical Components and Laws

• A node is a junction where two or more network elements are connected.
• A loop is a closed path for current flow in an electrical circuit.
• Dielectric strength is the voltage a dielectric material can withstand without breaking down.
• Magnetic flux density is the magnetic flux per unit area, measured at right angles to the flux path.
• Magnetic flux density is measured in weber/m² or tesla (T).
• Statically induced EMF is the electromotive force (EMF) induced in a stationary coil or conductor when the flux linked with it changes over time.
• Resistance opposes current flow, while resistivity is a material's property that resists current flow.
• For a material with high resistivity includes mica, nichrome, rubber, glass, plastic, porcelain and dry wood.
• Active networks contain an energy source while passive networks do not contain any energy source.
• A unilateral network's characteristics depend on the direction of current flow, and a bilateral network are independent of the direction of current flow through its elements.
• Reluctance is the opposition to magnetic flux in a magnetic circuit.

Resistors and Applications

• Carbon composition resistors are used in potential dividers, welding controls, power supplies, spark circuits, radio/TV receivers, transistor biasing, amplifier circuits, and zener voltage regulators.
• Metal film resistors are used in transmitter, telecommunications, and audio amplifier circuits, as well as oscillators, testing, and measurement applications.
• Wire wound resistors are used in power amplifiers, zener voltage regulators, and radio/TV receivers, and also in high power resistance DC power supplies and measurement circuits.
• High voltage ink film type resistors are used in C R O circuits, Radar, and medical electronics.
• Carbon film resistors are used for electronic circuits
• Cermet resistors are used in printers, automotive applications, computers, cell phones, and battery chargers.

Capacitor Types

• Air capacitors are used for radio tuning, antenna tuning, RF matching networks, MRI medical scanners
• Paper capacitors facilitate high voltage and high current applications
• Mica capacitors are used in high frequency tuned circuits, such as filters and oscillators
• Ceramic capacitors are used for tone compensation, automatic volume control filtering and more
• Electrolytic capacitors: Reduce voltage fluctuations in various filtering devices in input and output smoothing.

Electromagnetic Laws and Concepts

• Faraday's first law states that when a conductor cuts magnetic flux, an EMF is induced.
• Faraday's first law is used in generator and alternator principles.
• Fleming's right-hand rule is used to find the direction of dynamically induced EMF, relating the direction of motion, magnetic field, and induced current.
• Lenz's Law states the direction of an induced EMF opposes the cause producing it.
• Lenz's law is used for finding the direction of statically induced emf.
• Fleming's left-hand rule is used for finding the direction of force acting on a current-carrying conductor in a magnetic field.
• Hysteresis is when magnetic flux density lags behind the magnetizing force.