1.
In which direction does electric current flow around a circuit.
Correct Answer
C. Positive to Negative
Explanation
Electric current flows from the positive terminal of a power source to the negative terminal. This is because electrons, which carry the charge in a circuit, are negatively charged and are attracted to the positive terminal. Therefore, the flow of electric current is from positive to negative.
2.
When an electric current flows through a wire what is moving?
Correct Answer
D. Electrons move along along the wire
Explanation
When an electric current flows through a wire, it is the electrons that are moving along the wire. Electrons are negatively charged particles that carry the electric charge in a circuit. They move from the negative terminal of the power source towards the positive terminal, creating the flow of electric current. The movement of electrons is what allows electrical energy to be transferred from one point to another in the wire.
3.
A current of 2.5A flows through a light bulb with a potential difference of 10V applied across it. What is the resistance of the light bulb?
Correct Answer
B. 4 ohms
Explanation
The resistance of a device can be calculated using Ohm's Law, which states that resistance is equal to the potential difference across the device divided by the current flowing through it. In this case, the potential difference is 10V and the current is 2.5A. Therefore, the resistance can be calculated as 10V / 2.5A = 4 ohms.
4.
A 60 ohm heater is used in a car heating system. If a potential difference of 12V is applied, what is the current that flows through the heater.
Correct Answer
A. 0.2A
Explanation
The current flowing through a circuit can be calculated using Ohm's Law, which states that current (I) is equal to the potential difference (V) divided by the resistance (R). In this case, the potential difference is 12V and the resistance is 60 ohms. Plugging these values into the formula, we get I = 12V / 60 ohms = 0.2A. Therefore, the correct answer is 0.2A.
5.
Which of the following best describes the behaviour of a Thermistor.
Correct Answer
E. Its resistance decreases if the temperature increases
Explanation
A thermistor is a type of resistor whose resistance decreases as the temperature increases. This behavior is due to the fact that the electrical resistance of the thermistor is dependent on the temperature of its surroundings. As the temperature rises, the thermistor's resistance decreases, and as the temperature decreases, its resistance increases. This property makes thermistors useful in temperature sensing and control applications.
6.
An electrical device that will only let the electric current flow in one direction is called
Correct Answer
D. A Diode
Explanation
A diode is an electrical device that allows the electric current to flow in one direction only. It acts as a one-way valve for the flow of electricity, allowing current to pass through in one direction while blocking it in the opposite direction. This property of a diode makes it useful in various applications such as rectification, signal modulation, and voltage regulation.
7.
Two resistors are connected in series. If the resistors are 20 ohms and 30 ohms the total resistance of the circuit is
Correct Answer
D. 50 ohms
Explanation
When resistors are connected in series, their resistances add up to give the total resistance of the circuit. In this case, the resistances of the two resistors are 20 ohms and 30 ohms. Adding them together, we get a total resistance of 50 ohms.
8.
A 10 ohm resistor and a 50 ohm resistor are connected in parallel. The best description of the combined resistance is
Correct Answer
A. Less than 10 ohms
Explanation
When resistors are connected in parallel, the total resistance decreases. In this case, the 10 ohm resistor and the 50 ohm resistor are connected in parallel, so the combined resistance will be less than the smallest resistance value, which is 10 ohms. Therefore, the best description of the combined resistance is "Less than 10 ohms".
9.
In a parallel circuit the component with the largest resistance gets:-
Correct Answer
D. The least current
Explanation
In a parallel circuit, the component with the largest resistance gets the least current. This is because in a parallel circuit, the potential difference across each component is the same, but the current is divided among the different branches based on their resistance. The component with the largest resistance will have the least current flowing through it, as it offers more resistance to the flow of electrons compared to the other components.
10.
As the current through a filament light bulb, its resistance increases. The best reason for this is:-
Correct Answer
B. The filament gets hotter
Explanation
As the current passes through a filament light bulb, it heats up the filament. This increase in temperature causes the atoms within the filament to vibrate more vigorously, resulting in an increase in resistance. This phenomenon is known as the temperature coefficient of resistance, where the resistance of a material increases with an increase in temperature. Therefore, the best reason for the increase in resistance is that the filament gets hotter.