methods of producing emf

A set of flashcards covering the various methods of producing electromotive force (emf) including chemical, thermal, piezoelectric, photoelectric, electromagnetic, and electrostatic methods.

What does a basic battery consist of according to the transcript?

Two dissimilar metals and an electrolyte.

In a battery, what are the polarities assigned to the anode and the cathode?

The anode is always negative and the cathode is always positive.

How is voltage generated in a thermocouple circuit?

It is generated by using two different wires at different temperatures; different rates of electron flow in each wire create an imbalance at the connection.

The magnitude of the voltage generated by a thermocouple is approximately directly proportional to the temperature difference between which two points?

The hot junction and the cold junction.

What are the two main groups of piezoelectric materials?

Crystals and ceramic.

What is the 'converse piezoelectric effect'?

The effect where voltage is applied to the crystal or ceramic, resulting in mechanical movement.

According to the notes, what is the best-known piezoelectric material?

Quartz.

What is the maximum output of a photovoltaic cell mentioned in the transcript?

About $50\,mA$ at $2.5\,v$.

Based on the photoelectric effect, what is the relationship between the produced voltage and light intensity?

The voltage produced is directly proportional to the amount of light hitting the PN junction.

What is electromagnetic induction (or generator action)?

The process where an emf is developed in a conductor when it is moved through a magnetic field (or when the field is moved across a conductor).

What does Faraday's Law of Induction state regarding the magnitude of induced voltage?

It states that the magnitude of the induced voltage is proportional to the rate at which the conductor cuts the lines of force.

According to Faraday's Law, what rate of cutting lines of force induces one volt across a conductor?

100 million lines per second.

What three factors affect the value of induced voltage in a generator?

Flux density (strength of the field), the length of the conductor within the field, and the rate at which lines of force are cut.

What is the primary difference between a battery and a Van de Graaff generator in terms of electrical source characteristics?

Batteries are constant voltage devices, whereas Van de Graaff generators are constant current electrostatic devices.

What is tribocharging?

The separation of electric charges that occurs when two materials are brought into contact and then separated.

Describe the charge state of an atom that has an overall positive charge.

The atom has a greater positive charge in the nucleus and a deficiency of electrons.

What is the maximum voltage a Van de Graaff generator can produce?

As high as 20 million volts.

According to the transcript, which method of producing emf is the least utilized commercially?

Electrostatics generation.

How does a fuel cell work based on the self-test?

It harnesses the chemical reaction of combustion.