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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.....
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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
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.
What does a current flow of electrons need?
Your question is not clear. A current is generated when a group of electrons flow through a conductor, and this happens when there is a potential difference between the 2 ends of the conductor. If you want to know how can we start the flow of electrons it is by creating a potential difference in between the 2 ends of the conductor.
A difference between electric forces and gravitational forces is that electrical forces include?
Electro-magnetism, or the electromotive force - EMF.
What is the difference between CEMF and EMF?
Only the relative direction they are moving. EMF, measured in Volts, travels along a conductor, perhaps because a magnetic field has built up around the conductor. When that magnetic field collapses, CEMF, or counter-EMF is generated in the conductor, and it travels in the opposite direction of the original EMF, countering the original flow of electricity. EMF is Electromotive Force, and is one component of measuring electricity. EMF is measured in Volts, and represents the 'pressure' moving the electricity along.
Difference between voltage and emf?
'Voltage' is simply another term for 'potential difference', and an electromotive force is the open-circuit, or no-load, potential difference of a source such as a battery or generator.
Another name for EMF?
"Potential difference" or "Voltage".
Why volt meter is always placed in parallel?
Because the quantity it measures is 'EMF' or 'potential difference', that is,the difference in potential between two points. There may be 1 or 1,000circuit components between the two points.
What is the potential difference between two points in a circuit is called?
Voltage drop
When is the terminal potential difference of a battery greater than its emf?
When it is being loaded.
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 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.
What symbol is used to measure potential difference?
V which abbreviates the word volt, which is the unit of measure of the difference in electromotive force (EMF), (or electric potential) between two points of contact; the resulting voltage difference could be direct current (DC) or alternating current (AC) depending on the source of the voltage difference.
What unit would be used to measure the potential difference between two poles of a battery?
The volt.The volt.The volt.The volt.
Under what circumstances can the terminal potential difference of a battery exceed its emf?
"The potential difference between the terminals of a battery will equal the emf of the battery when there is no current in the battery. At this time, the current though, and hence the potential drop across the internal resistance is zero. This only happens when there is no load placed on the battery-that includes measuring the potential difference with a voltmeter! The terminal voltage will exceed the emf of the battery when current is driven backward through the battery, in at its positive terminal and out at its negative terminal." Raheel Ahmed Quaid i Azam University Islamabd Physics Dept
Factors affecting emf of electrochemical cells?
temperature,length of the wire,area,potential difference
What is Counter Force?
It is also called back EMF. Back EMF is the electric potential difference that opposes the current that induces it. See related link below.
