Final answer:
The 'quality' of electrons in terms of their kinetic energy is determined by the frequency of the incoming light and the material's work function, not by the electric current (mA). Several true/false statements related to physics concepts like the photoelectric effect, electric currents, and polarization have been addressed.
Step-by-step explanation:
The statement that 'mA controls the quality of boiled off electrons' appears to be a misphrased question about the control of electron emission in a photoelectric effect or similar context in physics. In such contexts, 'mA', referring to milliampere, is a unit of electric current and does not directly control the quality of the electrons emitted. The factors that control the 'quality', which could refer to the kinetic energy of the ejected electrons, are the frequency of the incoming light and the material's work function, not the current.
Let's address the relevant statements for a clearer understanding:
- Photoconductive cell current creation: A current is indeed created in a photoconductive cell when at least one electron is expelled from a photon strike, so the answer is true.
- Nonzero DC current from AC currents: It is false that a nonzero DC current can be produced by simply adding together AC currents, as AC currents average out to zero over time.
- Inducing electric current with a magnet: Dropping a bar magnet through a copper tube does indeed induce an electric current in the tube, which is an example of electromagnetic induction, making this statement true.
- Voltage in a circuit diagram: Within a circuit diagram, and in practice, the voltage is not the same at every point in a given wire due to the potential drop across components, so this claim is false.
- Polarization and charging: Charging an object by polarization does not require direct contact with a charged object, as polarization can happen due to the electric field of the nearby charged object. Therefore, this statement is false.
- Photoelectric effect and light brightness: The kinetic energy of ejected electrons in the photoelectric effect is related to the energy (frequency) of the photons, not the brightness (intensity) of the light. Therefore, increasing brightness without increasing frequency will not increase electron kinetic energy, making this claim false.