basic terms

[sundar]

i have searched the explanation of these terms in google..but i was still not clear about it.
i) what happens when a capacitor is connected in series and in parallel?
what is the effect of impedance on a capacitor ?is this the same as resistance?

ii) what is bleeding resistor,steering diode,current source?where and when do we need it?

 

[ericgibbs]

i have searched the explanation of these terms in google..but i was still not clear about it.
i) what happens when a capacitor is connected in series and in parallel?
Assume your caps are 1uF,
Connecting two in Series, would give an overall capacitance of 0.5uF, in parallel 2uF

what is the effect of impedance on a capacitor ?is this the same as resistance?
Impedance of an ideal capacitor is a function of the frequency of the alternating voltage applied across the capacitor.
Xc = 1 / [2*pi *freq *cap)

ii) what is bleeding resistor,steering diode,current source?where and when do we need it?
A bleed resistor across the cap is used to discharge the cap when the supply voltage is switched OFF
A steering diode is used to control the direction of flow of current in a circuit.
A current source has to be defined in the context of the circuit that you are using... the question is too general.

hi,
Does this help.??

 

[crutschow]

To elaborate on Eric's current source comment:

There are two basic types of power sources in electronics: constant voltage and constant current.

A constant voltage source is the most common, such as a battery, a DC generator, or the typical supply for an electronic circuit. In that case the voltage is constant and the circuit takes whatever current it needs to operate.

A constant current source is used for a few specialized requirements where the load operates better with a specified current rather than a voltage. It is generally provided by an electronic circuit designed to generate a constant current output. (Interestingly, the circuit usually derives its power from a constant voltage source.) With a constant current source the output current is constant and the voltage depends upon the load characteristics. Examples are powering LED circuits and charging certain types of batteries such as NiMH.

A typical lab supply with an adjustable current limit can be used as a constant current source by turning the voltage to the maximum and adjusting the current limit to the desired current. The output will then be a constant current up to the voltage limit of the supply.

An interesting example of a constant current mechanical generator is a Van de Graaff machine. When in operation it generates a constant current into the capacitance of the ball until it arcs over and generates a large spark.

 

[sundar]

basics help..

thanks for your explanation ..,
but still i am having a doubt
what is the purpose of using a capacitor in (series or parallel) to the supply?whether it is used to bypass or for charging purpose?.in many cases i have used ceramic capacitor (of range 0.47 nf,0.01 nf) .is that used for charging or for anything else?

 

[k7elp60]

thanks for your explanation ..,
but still i am having a doubt
what is the purpose of using a capacitor in (series or parallel) to the supply?whether it is used to bypass or for charging purpose?.in many cases i have used ceramic capacitor (of range 0.47 nf,0.01 nf) .is that used for charging or for anything else?

When capacitors are put in series two things happen. 1. The total capacitance of the two capacitors is reduced, total (1/CT=((1/C1)+(1/C2)). The total working voltage is increased. The working voltages are simply added.

When capacitors are put in parallel the resulting capacitance is = to the sum of the individual values. The working voltage is = to the lowest working voltage.
If time constants are involved the time a capacitor takes to charge to specific voltage is the key. When the capacitor is used for a bypass its capacitive reactance comes into play, and generally a frequency or range of frequencies is considered for a capacitor value.
A capacitor's function is to oppose a change in voltage. It does this by discharging if the voltage of the circuit starts to decrease. By discharging it tries to keep the voltage constant. Since it takes time for the capacitior to discharge it may go to 0 volts or may only discharge slightly depending upon the overall circuit. If the voltage of the circuit tries to increace the capacitor charges absorbing the voltage increase. The capacitor my only charge slightly, or it may charge fully to the new voltage depending upon the circuit.

 

[crutschow]

When capacitors are put in series two things happen. 1. The total capacitance of the two capacitors is reduced, total (1/CT=((1/C1)+(1/C2)). The total working voltage is increased. The working voltages are simply added.

That's only true if the capacitance values are equal (and even then the voltage may not split evenly due to differences in capacitor leakage). Otherwise the voltage is split such that the smaller capacitor takes a larger percentage of the voltage. It's good design practice to have the maximum total voltage level across the series capacitors no greater than the working voltage of any one capacitor in the series string.

 

[ronv]

I think I may know where you are going. There are many types of capacitors and each has some things that may make it better for a certain application. For example you may see a .01 ufd. ceramic cap in parallel with a 47 ufd. electrolytic cap. The .01 is good for high frequency because it has low inductance while the electolytic can supply more capacitance than is easy to make with ceramic. Together in parallel you can get the benifits of both.