Questão 1
Questão
Consider the alternating current (Fig. 3). What fraction of its period (T) does it take to reach from zero to half of its amplitude?(hint: sin300=1/2)
Questão 2
Questão
What particles are the electric current carriers (charge carriers) in metals?
Responda
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Electrons
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Ions
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Electrons and holes
Questão 3
Questão
For the photoelectric effect to take place, the wavelength (λ) of the incident light must satisfy the following inequality:
Where: ɸ is the minimum energy needed to remove an electron from metal (work function); h is Plank constant.
Responda
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λ ≥ ɸ/h
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λ ≤ hc/ ɸ
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λ ≥ c/ɸ
Questão 4
Questão
Electric current is measured in units of amps (A) which represent the following rate of change:
Responda
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Charge per time, Q/t
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Energy per charge, E/Q
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Energy per distance, E/x
Questão 5
Questão
Alternating current (AC):
Questão 6
Questão
The Oscilloscope measures and displays the relationship between two variables, input (y-axis) andreference (x-axis). Choose the correct pair:
Responda
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Time (input) vs Voltage (reference)
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Voltage (input) vs Time (reference)
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Current (input) vs Voltage (reference)
Questão 7
Questão
The current carriers inside vacuum tubes are:
Responda
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Electrons
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Ions
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Electrons and holes
Questão 8
Questão
The term ”charge carrier” refers to
Responda
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Strictly to electrons and holes
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Strictly to electrons and protons
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Any particle that has an electric charge
Questão 9
Questão
The term ”elementary charge“ refers to
Responda
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The charge of the electron
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The charge of any charge carrier
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The charge of any elementary particle
Questão 10
Questão
If across 25Ohm resistor is applied 50V (DC) how many Amperes is the current that will flow:
Questão 11
Questão
What happens to the current (DC) in metallic conductor, if the voltage is doubled?
Responda
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It will be halved
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It will double
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It will stay the same
Questão 12
Questão
Ohm’s Law states that the magnitude of the electric current is proportional to the applied voltage and inversely proportional to the resistance in the conducting material. Choose one:
Questão 13
Questão
For Ohmic load in a DC circuit, what would be the change in power consumption if the voltage is halved?(hint: in Ohmic circuits the ratio V/I = constant, and power = V·I)
a. It will double
Responda
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It will double
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It will be halved
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It will be quartered
Questão 14
Questão
What is the resistance in a load if, when 120 V are applied, it draws a current of 20 Amps:
Questão 15
Questão
Metals are good conductors of electricity because:
Questão 16
Questão
A 400 Ohm resistor draws 0.05 A direct current. What is the voltage across the resistor