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Yes. Let's look at an example.
A 12 volt system can operate a 12 volt relay coil to actuate the plunger. But when the field of the coil collapses in the instant following when the coil is de-energized, the collapsing field can generate an "inductive kick" that can easily reach several hundred volts.
Relay coils frequently have diodes across their coils to shunt this voltage through the coil and prevent it reaching other parts of the circuit because it is a higher voltage and could damage components.
As a closing note, you're not "getting something for nothing" or generating more energy out of the coil than originally went in. The power in still equals the power out (less any loss). With a properly designed coil utilizing Marko Rodin's configuration, losses are negligible.
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What happens to the generated voltage of a self excited generator if shunt field resistance is greater than the critical resistance?
it doesn't develop emf ..........
Three similarities between pd and emf?
Both emf and pd have the same unit. namely volt Both have the same definition. It is the work performed in moving unit positive charge right from one point to the other against the electric field. Both are got by the product of current and resistance. But emf is the pd across of a cell or source when it is not in action. So emf is slightly greater than the pd in the circuit as there may be a little bit of internal resistance.
What is the Opposition to current flow in a inductive ac circuit?
Back EMF.
Why current decreases when increase in viscous friction of dc motor?
I think your question could be rephrased as:"When viscous friction increases, why does currentdecrease?". Though the latter is not directly dependent on the former, or vice versa, in most motors this is the case. To understand exactly why this happens we need to look into the constructional features of a motor.All motors have a rotor (the spinning part) and a stator (the stationary part). In linear motors the part the slides along can be thought of as the 'rotor', and the non-moving base, as the 'stator'. The motor spins by causing like poles on the stator and rotor to oppose each other (different motors - AC, DC, brushless - do this in different ways). Read up about this on Wikipedia, HowStuffWorks, or just Google around. For maximum efficiency it is desirable to build the rotor and stator in such a way that there is very little space between the two. This allows a high degree of magnetic flux linkage/concentration between the rotor and stator. Between the rotor and stator is a small air gap. Air, like all fluids, has viscosity (a sort of 'stickyness', if you will). Viscous force appears between two sliding objects which have a liquid in between them. The closer the sliding surfaces, the greater is the viscous force. Viscous force also depends on the area of the surfaces, their relative velocity, and the liquid's properties. For a detailed derivation please refer to any text on fluid dynamics.Another important motor characteristic is back EMF (BEMF), which is induced in motor coils due to magnetic interaction. The faster a rotor spins, the greater the magnitude od back EMF. Back EMF, as its name suggests, has a polarity opposite to the applied (battery/power source) EMF. It is the back EMF which causes a reduction in motor current, since it partially cancels out the applied EMF : (Applied EMF-Back EMF)=(Effective EMF). Since the coils in the motor have unchanging resistance, a lower apparent EMF imples lower current.Now let us link these two phenomena:low speed-->low BEMF-->high currentalso;low speed-->low viscous frictionbut:higher speed-->higher BEMF-->lower currentand:higher speed-->higher viscous frictionI hope this clears things up.Rohit de Sa,Engineer,Mercedes-Benz,INDIA
What are the differences between emf and voltage drop?
emf and voltageAnswerElectromotive force is the potential difference created by a source, such as a battery or generator, when it is not connected to a load -in other words, on 'open circuit'.Voltage drop is the potential difference across a load, such as a resistor, which causes current to flow through that load.A voltage drop occurs, internally, in batteries and generators, when they are supplying a load. The battery or generator's terminal voltage, when supplying a load, is its e.m.f. less its internal voltage drop.
Why emf of battery driving potentiometer is greater than emf of the cell to be measured?
Bcoz the emf which is to be measured is less than emf of driving cell....
What are the differences between potential difference and emf?
emf is present mainly in battery and potential difference is mainly present in circuit. emf is greater than p.d and p.d is greater than emf.......the units of both are Volt.....
When is the terminal potential difference of a battery greater than its emf?
When it is being loaded.
Can the terminal voltage of a battery be larger than its emf?
the voltage of a battery could be larger than the emf if you are to charge the battery, in that case V=E+Ir .
Is potential difference always less than emf of the cell?
No. Because during charging process of a battery current flows in opposite direction to the discharging/consumption. so equation Emf=P.d. +Ir is changed to Emf=p.d. +Ir. Hence during charging process of a battery Potential difference is greater than electromotive force.
While discharging which is greater TPD or EMF?
EMF is greater
How do you connect a voltmeter to a battery?
To measure the total emf simply connect the battery and voltmeter with the right terminals , but to measure the terminal potential difference which is less than the emf the voltmeter is connected in parallel with the battery
Can the potential difference across a battery be greater than its EMF?
If the emf of a battery is E Volt, the potential difference across a battery is given byV = E -I r where I is the current in the circuit and r is the inetrnal resistance.Hence E and V will be equal only when I = 0.The maximum potential difference across the battery will be equal to E only if I = 0.In gnereral potential difference can be equal or less than the emf.E.m.f can never exceed the potential difference.=====================================A battery charger is a device used to put energy into a secondary cell or (rechargeable) batteryby forcing an electric current through it.Hence to charge a battery another source of emf is needed.The combined emf is now will be (E - E1) where E is the emf of the battey in quesiton and E 1 is the emf of the external source used to charge the battery.Note that E-E1 will be negative in sign.======================================...A battery is charged only when its emf is less than its maximum emf.Suppose that the maximum emf of a cell is 1.5V. The battery should be charged only when its emf is less than 1.5 V say 0.5 V.To charge the cell we use a different source of emf E1 say 3V.The positive of the second source is connected to the negative of the cell so that theCombined emf is now 0.5 - 3 = -2.5V.The negative sign indicates that the emf is opposite to the emf of the cell which is 0.5V.Since the cell is getting charged, the difference in emf is gradually reduced to zero when the cell is fully charged.In modern charging units there are provisions so that the cell is never allowed to be over charged, even if the charging unit is in on for about 12 hours.When the cell is fully charged, (that is when the emf of the cell is now 1.5V), the potential difference between either the second source or cell will be zero.Taking into consideration the sign of the emf and the direction of current through the cell and the sign of the potential difference, the potential difference will be always less than the emf of the cell (which gradually increases while charging).Note that the potential difference is negative if the emf of the cell is taken as positive.Also note that the cell is charged only when its emf is less than its maximum e.m.f
What happens to emf as a battery is used?
The emf of a batter as it is used will stay the same.
How do you prove the existence of back EMF?
How do you proof of the existence of back emf ?
What is the amount of push provided by the battery?
The amount of "push" provided by a battery is its electromotive force (emf). In common alkaline batteries, the emf is 1.5 volts.
what will be the emf of the battery when Four cells each of emf E are joined in parallel to form a battery?
E. Joined in parallel, the voltage (or electromotive force, "emf") isn't additive. You'd get four times the current, or four times the life of a single battery, but it would have the same voltage.
