DC circuits

Question 1

What is the relationship between current and voltage in a material that obeys Ohm’s Law?

Answer 1

The current through a material at a constant temperature is directly proportional to the voltage across it. This means that if you triple the voltage, the current will also triple.

Question 2

What is necessary for the resistance of materials obeying Ohm’s Law to remain constant?

Answer 2

The temperature must remain constant for the resistance of materials obeying Ohm’s Law to remain constant.What does Kirchhoff’s Current Law state?

Question 2

What remains constant for a given piece of material when it follows Ohm’s Law?

Answer 2

The quotient of voltage to current, which is called resistance, remains constant for a given piece of material when it follows Ohm’s Law.

Question 2

What is the formula representing Ohm’s Law?

Answer 2

The formula representing Ohm’s Law is V=IR, where
V is the voltage in volts (V), I is the current in amperes (A), and R is the resistance in ohms (Ω).

Question 3

What does Kirchhoff’s Current Law state?

Answer 3

Kirchhoff’s Current Law states that at any junction in an electrical circuit, the sum of currents flowing towards that point is equal to the sum of currents flowing away from it.

Question 3

In what units is resistance measured?

Answer 3

Resistance is measured in ohms (Ω).

Question 4

What does Kirchhoff’s Voltage Law state?

Answer 4

Kirchhoff’s Voltage Law states that the algebraic sum of all voltages around any closed loop in a circuit is zero.

Question 5

How can Kirchhoff’s Current Law be used in a circuit?

Answer 5

Kirchhoff’s Current Law can be used to calculate unknown currents at a branching point in an electrical circuit.

Question 6

What is the significance of Kirchhoff’s Voltage Law in a circuit?

Answer 6

Kirchhoff’s Voltage Law ensures that the total voltage around any closed loop in a circuit is zero, meaning that the voltage supplied is completely dropped across the components within the loop.

Question 7

What is important to remember about voltage in Kirchhoff’s Voltage Law?

Answer 7

It is important to remember that voltage doesn’t exist at any single point but is a difference in potential between two points.

Question 8

What is EMF in the context of a power source?

Answer 8

EMF (Electromotive Force) is the voltage provided by a power source such as a battery.

Question 9

What happens to the terminal voltage when the switch is open?

Answer 9

When the switch is open, the terminal voltage is equal to the EMF because no current flows through the internal resistance (IR).

Question 10

What happens to the terminal voltage when the switch is closed?

Answer 10

When the switch is closed, the terminal voltage is lower than the EMF because a current flows through the internal resistance (IR), creating a voltage drop across it.

Question 11

What is the formula for terminal voltage when the supply is on-load?

Answer 11

The formula for terminal voltage when the supply is on-load is V=EMF−I x r where
V is the terminal voltage, I is the current, and r is the internal resistance.

Question 12

What is short-circuit current?

Answer 12

Short-circuit current is the high current that flows when the terminals of the supply are directly connected, limited only by the internal resistance of the power source.

Question 13

Why can short-circuit currents be dangerous?

Answer 13

Short-circuit currents can be dangerous because they are very high and can quickly destroy a power source, potentially causing fires or other hazards.

Question 14

How does a battery’s internal resistance change over time?

Answer 14

A battery’s internal resistance increases as the battery discharges.

Question 15

How can you calculate a battery’s internal resistance?

Answer 15

A battery’s internal resistance can be calculated using the formula r = OCV − CCV/ I, where
OCV is the Open-Circuit Voltage, CCV is the Closed-Circuit Voltage, and I is the load current.

Question 16

What factors affect the terminal voltage of a power source?

Answer 16

The terminal voltage of a power source is affected by the size of the internal resistance and the amount of current flowing.

Question 17

Why is it important to observe the maximum current rating of a power source?

Answer 17

It is important to observe the maximum current rating of a power source to prevent damage to the power source and to avoid potential hazards such as fires or electric shocks.

Question 18

what does Kirchhoff’s first law state?

Answer 18

the total current flowing towards the node is equal to the total current flowing away from the node.

Question 19

a battery internal resistance (IR) is equal to the difference between the open-circuit voltage (OCV) and the closed-circuit voltage (CCV) divided by which quantity?

Answer 19

the current

Question 20

what can very high short-circuit current cause

Answer 20

they can quickly destroy a power source