Electrical Engineering Answers

The current in an electric lamp is 5 A. What quantity of electricity flows towards the filament in 6 minutes?

Consider a message signal 𝑚(𝑡) with bandwidth 𝑊 = 2 𝑘𝐻𝑧 , applied to a DSB-SC modulator, s.t., 𝑠(𝑡) = 𝐴𝑐𝑚(𝑡) cos(2𝜋𝑓𝑐 𝑡). Assuming perfect synchronism between the carrier waves in the modulator and detector. a. Determine (sketch) the spectrum of the detector output when 𝑓𝑐 = 1 𝑘𝐻𝑧. (Note: 𝑀(𝑓) is shown in the figure, and 𝑀(0) = 1.) b. Find the lowest 𝑓𝑐 for which each component of the modulated wave 𝑠(𝑡) is uniquely determined by 𝑚(𝑡). Sketch the spectrum of the detector output with the lowest 𝑓𝑐 that you have required. 

The average value of an oscillating electric current over one period may be zero. For example, 2nt suppose that the current is described by a simple sinusoid: i(t) = sin 2πt/T where T is the period.

The average value of this function can be determined by the following equation:

i=∫ν0^T(2πt/T)dt/T-0 = -cos(2π) + cos0/T=0

Despite the fact that the net result is zero, such current is capable of performing work and generating heat . Therefore, electrical engineers often characterize such current by

I RMS = √1\T∫ν0^Ti^2(t)dt

where i(t) = the instantaneous current. Calculate the RMS or root-mean-square current of the waveform shown in following figure using the trapezoidal rule, Simpson's 1/3 rule, Simpson's 3/8 rule for T =1 s taking n = 6.

A parallel plate capacitor is made of 250 plates separated by a

dielectric 0.0012cm thick. The effectíve size of thé plate is 12cm x

24cm. If the dielectric constant is 2.5, what is the capacitance of

this capacitor?

Each electrode of a capacitor of the electrolytic type has an area o

0.02㎡,The relative permittivity of the dielectric aim is 2.8. if the

capacitor has a capacitance of 10uf, estimate the thickness of the

dielectric film. 

A parallel-plate capacitor, having plates of 100c㎡ and has three

dielectrics 1mm each and of permittivity’s 3, 4 and 6. If the peak

voltage 2000V is applied to the plates, calculate the energy stored

in each dielectric

Find the capacitance per unit length of a cylindrical capacitor of

which the two conductors have a radius of 2.5 cm and 4.5cm and the

dielectric consist of two layers whose cylinder or contact is 2.5cm .

radius, the inner layers having a dielectric constant of 4 and the

outer 6. 

Two capacitors C1 and C2 of 1μf and 3μf are connected in parallel

across a voltage supply. At a particular instant when the applied

voltage is increasing positively, the two capacitors together draw a

current of 4A. Find the instantaneous rate of increase of potential

across them. 

The oil dielectric to be used in a parallel plate capacitor has a

relative permittivity of 2.3 and the maximum working potential

gradient in the oil is not to exceed 104 V/m. Calculate the

Approximate plate area required for a capacitance of 0.0003μF,the

Maximum working voltage being 10,000 volts.

Two slabs of material of dielectric strengths 4 and 6 and of

thickness 2mm and 5mm respectively are the inserted between the

plates of a parallel plate capacitor. Find how much the distance

between the plates should be changes so as to restore the potential

of the capacitor to its original value.