Exam 31: Electromagnetic Oscillations and Alternating Current

In an oscillating LC circuit, the total stored energy is U and the maximum charge on the capacitor is Q.When the charge on the capacitor is Q/2, the energy stored in the inductor is:

In an RLC series circuit, the source voltage is leading the current at a given frequency f.If f is lowered slightly, then the circuit impedance will:

A resistor, an inductor, and a capacitor are connected in parallel to a sinusoidal source of emf.Which of the following is true?

A 45-mH inductor is connected to an ac source of emf with a frequency of 400 Hz and a maximum emf of 20 V.The maximum current is:

A charged capacitor and an inductor are connected in series.At time t = 0 the current is zero, but the capacitor is charged.If T is the period of the resulting oscillations, the next time, after t = 0 that the current is a maximum is:

A charged capacitor and an inductor are connected in series.At time t = 0 the current is zero, but the capacitor is charged.If T is the period of the resulting oscillations, the next time, after t = 0 that the energy stored in the magnetic field of the inductor is a maximum is:

A coil has a resistance of 60 $\Omega$ and an impedance of 100 $\Omega$ .Its reactance is:

The rapid exponential decay in just a few cycles of the charge on the plates of capacitor in an RLC circuit might due to:

A sinusoidal voltage V(t)has an rms value of 100 V.Its maximum value is:

Consider the mechanical system consisting of two springs and a block, as shown.Which one of the five electrical circuits (I, II, III, IV, V)is the analog of the mechanical system?

An RLC circuit has a resistance of 200 $\Omega$ an inductance of 15 mH, and a capacitance of 34 nF.At time t = 0 the charge on the capacitor is 25 µC and there is no current flowing.After five complete cycles the energy stored in the capacitor is:

A 45-mH inductor is connected to an ac source of emf with a frequency of 250 Hz and a maximum emf of 20 V.If the voltage across the inductor is zero at time t = 0, what is the voltage at time t = 2.0 ms? Assume the phase constant is zero.

A charged capacitor and an inductor are connected in series.At time t = 0 the current is zero, but the capacitor is charged.If T is the period of the resulting oscillations, the next time, after t = 0 that the energy stored in the electric field of the capacitor is a maximum is:

Which of the following has the greatest effect in decreasing the oscillation frequency of an LC circuit? Using instead:

In a series RLC circuit the rms value of the generator emf is and the rms value of the current is i.The current lags the emf by $\phi$ .The average power supplied by the generator is given by:

A power transmission line carries 400A of current at a voltage of 765 kV.If the line has a resistance of 29 µΩ/m, what is the rate at which energy is being dissipated in 800 km of line?

Iron, rather than copper, is used in the core of transformers because iron:

A capacitor in an LC oscillator has a maximum potential difference of 15 V and a maximum energy of 360 $\mu$ J.At a certain instant the energy in the capacitor is 40 $\mu$ J.At that instant what is the potential difference across the capacitor?

In a purely resistive circuit the current:

The primary of a 3:1 step-up transformer is connected to a source and the secondary is connected to a resistor R.The power dissipated by R in this situation is P.If R is connected directly to the source it will dissipate a power of: