Electricity Flashcards
What is the definition of emf?
EMF is the energy supplied by the cell to each coulomb of charge
What is the definition of current ?
Current is the number of coulombs of charge passing a point in 1 second
What is the definition of capacitance?
Capacitance is the amount of charge stored per volt.
What is a.c.?
a.c. is alternating current - direction & instantaneous value of current is continuously changing.
What is the definition of potential difference?
Potential difference is the number of joules of energy transferred per coulomb of charge.
What is the unit for capacitance (C)?
farads F
What is the unit for charge (Q)?
coulombs, C
What is the unit for potential difference (V)?
volts V
How would you calculate the peak voltage of the signal shown on the oscilloscope screen?
Measure the amplitude (the distance from centre line to the peak), and multiply this by the “volts per division”
What is the definition of r.m.s. voltage (Vrms)?
The r.m.s. voltage (Vrms), or the root mean square voltage, is the value of an a.c. voltage which will deliver the same amount of energy as a d.c. voltage
What is meant by an ‘open circuit’?
An open circuit is one in which a current is not flowing (e.g. when a switch is open).
What is meant by a ‘short circuit’?
A short circuit is one in which there is no external resistance.
From the graph shown, how would the emf be obtained?
The emf is the intercept on the y-axis (the potential difference axis).
From the graph shown, how would the internal resistance be obtained?
The internal resistance is equal to the negative of the gradient of the graph.
From the graph shown, how would the short-circuit current be obtained?
The short-circuit current is the intercept on the x-axis (the current axis).