0
Can the potential difference across a battery be greater than its EMF?
Wiki User
∙ 10y ago
If the emf of a battery is E Volt, the potential difference across a battery is given by
V = 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 the
Combined 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
Wiki User
∙ 10y ago
Add your answer:
Earn +20 pts
Is potential difference directly or inversely proportional to resistance?
Potential Difference (V) across two resistors is directly proportional to the resistance (R) as greater the potential difference, greater is the resistance and vice versa.
What is the potential difference in electricity?
The potential difference in electricity is the Electromagnetic Force, in Volts, measured across the two wires that make the circuit.
When a 12 V battery ie a battery of EMF 12 V is connected across a lamp with a resistance of 6.8 ohms the potential difference across the lamp is 10.2 V Find the current through the lamp?
The idea is to use Ohm's Law (V=IR). In this case, the relevant voltage is the 10.2 V across the lamp.
What happen is the potential difference across is double?
If the potential difference between the ends of any conductor is doubled, then the current through the conductor is also doubled.
Can terminal potential difference be greater than the emf supplied?
All cells have internal resistance. When connected to a load, the resulting load current results in an internal voltage drop across the internal resistance. This voltage drop acts in the opposite sense to the cell's e.m.f., thus causing its terminal voltage to fall below that of the e.m.f. The greater the load current, the greater the difference between the terminal voltage and the e.m.f.
What is the potential difference across the terminals of a battery?
Please share your answer?
Is potential difference directly or inversely proportional to resistance?
Potential Difference (V) across two resistors is directly proportional to the resistance (R) as greater the potential difference, greater is the resistance and vice versa.
Why does a battery work?
A battery s a source of constant potential difference , this potential difference drives the electrons present in the wire and this constitutes current .Shortly the potential difference across the battery terminals does work on the conduction electrons present inside the conductor. Actually a battery is an electrolytic device ,after some time the electrolyte completely exhausts this state of battery is called as discharged state.
How is the potential difference maintained across the end of the conductor?
That's the job of the battery or other power supply.
What is terminal PD?
A terminal potential difference is the potential difference appearing across the terminals of a voltage source, such as a battery or a generator, which varies according to the load supplied.When the battery or generator is off load (i.e. no load is connected to it), the terminal potential difference is equal to the electromotive force of that battery or generator.The terminal potential difference tends to decrease as the load current increases, due to a corresponding increase in the internal voltage drop of the battery or generator.
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
A step-down transformer has 525 turns in its secondary and 12500 turns in its primary If the potential difference across the primary is 3510 V what is the potential difference across the secondary?
The potential difference across the secondary coil will be 147.42 Volts
What is the PD across two resistors connected parallel to a battery of emf 6V?
The potential difference across two resistors connected in parallel to a battery with a potential difference of 6 volts is 6 volts. Kirchoff's Voltage Law: The signed sum of the voltage drops in a series circuit is zero. This means that that the two series circuits involving the battery and each resistor have the same voltage across each other, and the series circuit involving the two resistors have the same voltage across each other.
Name a device that helps to maintain a potential difference across a conductor?
volt meter is the device that helps to maintain a potential difference across a conductor
What is the potential difference across a single 4 Ohm resistor if the source voltage is 230v?
the potential difference across the single 4ohm resistor is 230volts.
What is the potential difference across a 1500 ohm resistor carrying a current of 0.075 A?
Potential Difference across a resistor is given by, Potential Difference = Resistance * Current = 1500 * 0.075 = 112.5 Volts
What is difference between voltage and emf?
An electromotive force (e.m.f.) is the open-circuit, or no-load, potential difference provided by a source -such as a battery or generator. For a closed circuit, an e.m.f. is the sum of the voltage-drops around any closed loop, including the internal voltage drop of the source.A potential difference (voltage) can exist across any circuit component. For example, the fact that current is flowing through each of several resistors in a series circuit means that there must be an individual potential difference across each of those resistors (which we also term 'voltage drop').An electromotive force is the name we give to the open-circuit potential difference provided by a generator, battery, etc. For example, the open circuit potential difference of a battery would be its electromotive force.So, if we use a series resistive circuit as an example, the battery would provide the electromotive force, while voltage drops would then appear across its internal resistance, and across each of the resistances. The magnitude of the electromotive force is then equal (but acting in the opposite sense) to the sum of the voltage drops, including the internal voltage drop.Many textbooks use the symbol, E, to represent an electromotive force, and V to represent potential difference. So, Kirchhoff's Voltage Law, for example, will often be seen written as: E = V1 + V2 + V3 + etc.
