Does the direction of EMF depend on direction of current?
Direction of EMF is decided by the construction of the battery cell, it does not depend upon the direction of the current flow. In fact direction of the current flow depends upon the direction of emf. However direction of the voltage drop depends upon the direction of the current.
Is EMF opposite to current?
Counter-electromotive force (counter EMF, CEMF), also known as back electromotive force (back EMF), is the electromotive force or “voltage” that opposes the change in current which induced it. CEMF is the EMF caused by magnetic induction (see Faraday’s law of induction, electromagnetic induction, Lenz’s law).
Is EMF of a cell scalar or vector?
Electromotive force (EMF) is a scalar quantity.
Under what circumstances can the terminal potential difference of a battery exceed its EMF?
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.
Which condition EMF of cell is less than of terminal voltage?
Because emf is the potential difference across the two terminals of a voltage source when it is not connected to any circuit. And once it is connected to a circuit, the voltage reduces slightly because of the internal resistance of the voltage source.
Why current is not possible without EMF source?
emf is the potential difference across the two poles of a cell . hence without emf , no electric field will exist and hence no current will flow . …
Can potential difference be greater than EMF?
The potential difference across a battery cannot be greater than its emf. Basically, emf is the maximum potential difference between the terminals of a battery when the terminals are not connected externally to an electric circuit.
Can EMF be less than terminal voltage?
Yes it can, for example when a cell is being recharged the terminal pd is V=E+IR where E is the emf of the cell, I is the current passing through the cell from positive to negative terminal and R is the internal resistance of the cell.
Can Terminal PD be greater than EMF of cell?
In case when no current is drawn from the cell (in open circuit), the terminal p.d. is equal to the emf. In this process current flows from positive electrode to negative electrode inside the cell and terminal potential difference becomes (V = emf + Ir ) greater than the cell emf.
On what factors EMF of a cell depends?
E.m.f. of a cell depends upon the material of electrodes and electrolyte used in the cell. It is independent of shape of electrodes, distance between electrodes and the amount of electrolyte.
Can you measure EMF of a cell with a voltmeter?
The electromotive force (emf) of a cell is its terminal voltage when no current is flowing through it. The terminal voltage of a cell is the potential difference between its electrodes. A voltmeter cannot be used to measure the emf of a cell because a voltmeter draws some current from the cell.
How do you find the emf of a battery?
If we know the resulting energy and the amount of charge passing through the cell. It is the simplest way to calculate the EMF. The electromotive force of cell….The Formula for Calculating the EMF.
| \varepsilon | electromotive force |
|---|---|
| E | the energy in the circuit |
| Q | Charge of the circuit. |
Is it possible to measure the emf of a cell correctly using a voltmeter that draws a significant amount of current?
But Voltmeter draws apart of the current so there is an error in measurement of the potential difference. 2) Potentiometer can be used for measuring the internal resistance of a cell and also compare the e.m.f. of two cells , which cannot be done with a Voltmeter.
What is used to measure the emf of a cell?
The EMF of the cell can be determined by measuring the voltage across the cell using a voltmeter and the current in the circuit using an ammeter for various resistances.
What unit is EMF measured in?
volts
Which instruments measures EMF of a cell most accurately?
answer is potentiometer. as a voltmeter draws some current in cell it can not givethe accurate rating. a potentiometer is the best option as during the measurement by potentiometer no current flows through it.
When a resistor of 11ohm is connected in series?
When a resistor of 11Ω is connected in series with an electric cell, the current flowing in it is 0. 5A. Instead when a resistor of 5Ω is connected to the same electric cell in series, the current increases by 0.
What is the internal resistance of a cell?
Internal resistance refers to the opposition to the flow of current offered by the cells and batteries themselves resulting in the generation of heat. Internal resistance is measured in Ohms. The relationship between internal resistance (r) and emf (e) of cell s given by. e = I (r + R)
Which instrument is used to observe cells?
Microscopes
Which device measures internal resistance of a cell?
Potentiometer
What is electromotive force state its SI unit?
electromotive force = amount of. work done / quantity of charge. transferred. so, unit of emf = Joule/ coulomb. Also joule/coloumb is known to be equal to volt.
What is EMF write formula?
e = E/Q. Where, e = emf or electromotive force (V), W = Energy (Joules), and Q denotes charge (Coulombs). Both emf (electromotive force) and pd (potential difference) are measured in V (Volts) Electromotive force (emf) formula can also be written as, e = IR + Ir or, e = V + Ir.