Electricity

Question 1

What is the definition of emf?

Answer 1

EMF is the energy supplied by the cell to each coulomb of charge

Question 2

What is the definition of current ?

Answer 2

Current is the number of coulombs of charge passing a point in 1 second

Question 3

What is the definition of capacitance?

Answer 3

Capacitance is the amount of charge stored per volt.

Question 4

What is a.c.?

Answer 4

a.c. is alternating current - direction of current is continuously changing.

Question 5

What is d.c.?

Answer 5

d.c. is direct current - current flows in one direction only, negative to positive.

Question 6

What is the definition of potential difference?

Answer 6

Potential difference is the number of joules of energy transferred per coulomb of charge.

Question 7

What is the unit for capacitance (C)?

Answer 7

farads F

Question 8

How would you calculate the peak voltage of the signal shown on the oscilloscope screen?

Answer 8

Measure distance from centre line to top of wave (peak), and multiply this by the number of volts per division

Question 9

What is the definition of r.m.s. voltage (Vrms)?

Answer 9

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

Question 10

What is meant by an ‘open circuit’?

Answer 10

An open circuit is one in which a current is not flowing (e.g. when a switch is open).

Question 11

What is meant by a ‘short circuit’?

Answer 11

A short circuit is one in which there is no external resistance.

Question 12

What factors affect the time taken for a capacitor to charge (or discharge)?

Answer 12

increasing or decreasing the total resistance of the circuit.

Question 13

What are the majority charge carriers in n-type semiconductor material?

Answer 13

In n-type semiconductor, large number of free electrons is present. Hence, free electrons are the majority charge carriers in the n-type semiconductor. The free electrons (majority charge carriers) carry most of the electric charge or electric current in the n-type semiconductor.

Question 14

In semiconductors, what is meant by the term doping?

Answer 14

In semiconductor production, doping is the intentional introduction of impurities into an intrinsic semiconductor for the purpose of modulating its electrical, optical and structural properties

Question 15

In a p-n junction, what is meant by forward bias

Answer 15

Here, the voltage potential connections are as follows: -Ve (negative) to the N-type material and +Ve (positive) to the P-type material, across the diode. The effect is a decrease in the PN junction depletion layer.

Question 16

In a p-n junction, what is meant by reverse bias?

Answer 16

During this biasing condition, the voltage potential connections are as follows: +Ve (positive) to the N-type material and -Ve (negative) to the P-type material, across the diode. The result of this is an increase in the PN junction depletion layer.