Question 1

A voltage source's internal resistance is effectively in __________ with its external load&#10;A) series&#10;B) parallel&#10;C) series-parallel

Accepted Answer

The internal resistance of a voltage source is always in series with the external load. This is because the voltage source is essentially connected to the rest of the circuit via two terminals, which are connected in series with the internal resistance of the source.

Question 2

The potential difference appearing across a voltage source's terminals, when there is no load connected is termed its&#10;A) no-load voltage&#10;B) open-circuit voltage&#10;C) electromotive force&#10;D) any of the above

Accepted Answer

The terms "no-load voltage," "open-circuit voltage," and "electromotive force (EMF)" can all refer to the potential difference across a voltage source's terminals when there is no load connected, making any of these terms correct in this context.

Question 3

The potential difference appearing across a voltage source's terminals, when supplying a load, will be&#10;A) lower than its e.m.f.&#10;B) equal to its e.m.f.&#10;C) greater than its e.m.f

Accepted Answer

The potential difference appearing across the voltage source's terminals, when supplying a load, will always be lower than its e.m.f. This is because some energy is lost in the source's internal resistance while delivering the current to the load. Therefore, the voltage at the output of the source will always be slightly lower than its e.m.f.

Question 4

As the load increases, the terminal voltage of a voltage source will&#10;A) decrease further&#10;B) remain unaffected&#10;C) increase further

Accepted Answer

As the load increases, the internal resistance of the voltage source causes a drop in the terminal voltage. This means that the terminal voltage will decrease further.

Question 5

The sum of the voltage drops around any closed loop, including the internal voltage drop within a voltage source, is equal to the&#10;A) internal voltage drop&#10;B) e.m.f. of the voltage source&#10;C) external voltage drop

Accepted Answer

This is known as Kirchhoff's voltage law, which states that the algebraic sum of the voltage drops around any closed loop is equal to the e.m.f. of the voltage source. This means that the sum of all the voltage drops in a circuit must equal the energy supplied by the voltage source.

Question 6

A battery has an e.m.f. of 12 V and an internal resistance of 500 milliohms. What will be its terminal voltage, when supplying a load of 20 ohms?&#10;A) 0.293 V&#10;B) 11.7 V&#10;C) 12V

Accepted Answer

We can use the formula V = E - IR, where V is the terminal voltage, E is the EMF, I is the current flowing through the circuit, and R is the total resistance of the circuit. Since the load is 20 ohms, the total resistance of the circuit would be 500 milliohms + 20 ohms = 20.5 ohms.

We can solve for I using Ohm's law, which states that I = V/R. Plugging in the values, we get I = 12V/20.5 ohms = 0.585 A.

Now we can plug in all the values into the formula for V: 
V = E - IR 
V = 12V - 0.585 A x 500 milliohms 
V = 11.7V

Therefore, the terminal voltage of the battery when supplying a load of 20 ohms would be 11.7V.

Question 7

If the load supplied by the battery, described above, should increase, what will happen to its terminal voltage?&#10;A) It will decrease further&#10;B) It will remain unchanged&#10;C) It will increase

Accepted Answer

If the load supplied by the battery increases, the internal resistance of the battery will cause a voltage drop across the battery's terminals, resulting in a decrease in terminal voltage.

Question 8

What's likely to happen to the internal resistance of a generator when its load increases?&#10;A) It will remain the same&#10;B) It will increase, due to an increase in its temperature&#10;C) It will decrease, due to a decrease in its temperature

Accepted Answer

When the load on a generator increases, the current flowing through it also increases, which leads to an increase in the temperature of the generator. This increase in temperature also causes an increase in the internal resistance of the generator.

Deck 10: Internal Resistance of Voltage Sources