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Electric Circuits
A potentiometer wire of length 100cm has a resistance of 10Ω. It is connected in series to to a resistance R and a cell of emf 2V and negligible internal resistance. A source of emf of 10mV is balanced by a length of 40cm of the potentiometer wire. What is the value of the resistance R?
a. 200Ω
b. 950Ω
c. 2000Ω
d. 790Ω
a. 200Ω
b. 950Ω
c. 2000Ω
d. 790Ω
Electric Circuits
The half-life of a certain radioactive isotope is 32 hours. What fraction of the sample would remain after 16 huors?
a. 0.50
b. 0.25
c. 0.62
d. 0.71
a. 0.50
b. 0.25
c. 0.62
d. 0.71
Electric Circuits
A spectral line is emitted when an atom undergoes transition between two levels with a difference in energy of 2.4eV. What is the wavelength of the line?
a. 287nm
b. 507angstrome units
c. 377angstrome units
d. 518nm
a. 287nm
b. 507angstrome units
c. 377angstrome units
d. 518nm
Electric Circuits
When a copper surface is illuminated by radiation of wavelength 2537 angstrome units the value of the stopping potential is found to be 0.24volts. Calculate the work function of copper.
a. 4.48eV
b. 7.46eV
c. 3.26eV
d. 2.67eV
a. 4.48eV
b. 7.46eV
c. 3.26eV
d. 2.67eV
Electric Circuits
The work function of a metal is 3.45eV. Calculate the maximum wavelength of a photon that can eject photelectrons from the metal
a. 1.6×10^−6m
b. 3.6×10^−7m
c. 2.4×10^−8m
d. 3.4×10^−7m
a. 1.6×10^−6m
b. 3.6×10^−7m
c. 2.4×10^−8m
d. 3.4×10^−7m
Electric Circuits
An RLC circuit is used to tune a radio set to receive NOUN RADIO broadcasting at 105.9MHz in the FM band. The resistance and the inductance of the circuit of the radio set are 12Ω and 1.4μH respectively. What capacitance should the circuit have?
a. 1.64pF
b. 1.51μF
c. 1.33mF
d. 2.11pF
a. 1.64pF
b. 1.51μF
c. 1.33mF
d. 2.11pF
Electric Circuits
An ac circuit consists of a voltage source v=200sin120πt and a 6μF capacitor in series. Calculate the current established in the circuit.
a. 0.32A
b. 1.24A
c. 0.64A
d. 2.13A
a. 0.32A
b. 1.24A
c. 0.64A
d. 2.13A
Electric Circuits
A voltmeter connected across a 60Hz ac source reads 240V. Write down the expression of the instantaneous voltage as a function of time.
a. 240sin339.4t
b. 339.4sin377t
c. 377cos339.4t
d. 240cos339.4t
a. 240sin339.4t
b. 339.4sin377t
c. 377cos339.4t
d. 240cos339.4t
Electric Circuits
An air-cored transformer is assumed to be 100% efficient. The ratio of the secondary turns to the primary turns is 1:20. A 240V ac supply is connected to the primary coil and a 6Ω load is connected to the secondary coil. what is the current in the primary coil?
a. 0.10A
b. 0.14A
c. 2.0A
d. 40.0A
a. 0.10A
b. 0.14A
c. 2.0A
d. 40.0A
Electric Circuits
A proton with speed v perpendicular to a magnetic field B is experiences a force F. if the speed of the proton is doubled, the new force is
a. F/2
b. F
c. 2F
d. 4F
a. F/2
b. F
c. 2F
d. 4F
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#333702 on Dec 2022
#333702 on Dec 2022