1.
What is the unit for voltage?
Correct Answer
A. Volts
Explanation
The unit for voltage is volts. Voltage is a measure of the electric potential difference between two points in an electrical circuit. It represents the force or pressure that drives electric current through a conductor. Volts is the standard unit for measuring voltage in the International System of Units (SI).
2.
What is the unit for current?
Correct Answer
B. Amperes
Explanation
The unit for current is amperes. Amperes (A) is the standard unit for measuring electric current. It represents the rate at which electric charge flows in a circuit.
3.
What is the unit for resistance?
Correct Answer
C. Ohms
Explanation
The unit for resistance is ohms. Resistance is a measure of how much a material or device opposes the flow of electric current. It is represented by the symbol Ω and is named after the German physicist Georg Simon Ohm. The unit ohms represents the amount of resistance that reduces the electric current flow by one ampere when a voltage of one volt is applied.
4.
What is the unit for energy?
Correct Answer
D. Joules
Explanation
The unit for energy is joules. Volts, amperes, and ohms are units used to measure voltage, current, and resistance respectively, but they are not units of energy. Joules, on the other hand, is the standard unit for measuring energy in the International System of Units (SI). It represents the amount of work done or energy transferred when a force of one newton is applied over a distance of one meter.
5.
Which of these is the equation for Ohm's Law?
Correct Answer
B. V = IR
Explanation
Ohm's Law states that the voltage (V) across a conductor is directly proportional to the current (I) flowing through it, with the constant of proportionality being the resistance (R) of the conductor. This can be mathematically represented by the equation V = IR.
6.
What is shown in this picture?
Correct Answer
C. Resistors connected in series
Explanation
The picture shows resistors connected in series. In a series circuit, the components are connected one after another, creating a single pathway for the flow of current. In this case, the resistors are connected end to end, with the current passing through each resistor in succession. This arrangement increases the total resistance in the circuit, as the individual resistances add up.
7.
In the picture, how are the lightbulbs connected?
Correct Answer
B. In parallel
Explanation
The lightbulbs are connected in parallel. This means that each lightbulb is connected directly to the power source, creating multiple separate paths for the current to flow. In a parallel circuit, if one lightbulb stops working, the others will still remain lit because they are not dependent on each other.
8.
In the picture, how are the batteries connected?
Correct Answer
A. In series
Explanation
The batteries in the picture are connected in series. This means that the positive terminal of one battery is connected to the negative terminal of the next battery, creating a continuous loop. In a series connection, the voltage of the batteries adds up, while the overall capacity remains the same.
9.
What are these?
Correct Answer
C. Resistors
Explanation
These are all electronic components used in circuits. Batteries provide electrical energy, capacitors store electrical charge, resistors limit the flow of current, and transformers transfer electrical energy between circuits. Resistors specifically are used to control the amount of current flowing through a circuit by providing resistance to the flow of electrons.
10.
What do the stripes indicate?
Correct Answer
A. Amount of resistance
Explanation
The stripes on a component typically indicate the amount of resistance it has. Each color represents a specific value, and by reading the color code, one can determine the resistance value of the component. This is a common practice in electronics and helps in identifying and using the correct components for a circuit.
11.
In this circuit diagram, what are R_{1}, R_{2}, and R_{3}?
Correct Answer
D. Resistors connected in parallel
Explanation
The circuit diagram shows three resistors connected in parallel. This means that the current flowing through each resistor is the same, while the voltage across each resistor may be different. In a parallel circuit, the total resistance is less than the smallest individual resistance, and the total current is equal to the sum of the currents flowing through each resistor.
12.
Why can birds sit on a power line?
Correct Answer
D. Because both feet are on the same voltage line, so there is no potential difference, so current does not flow through the bird
Explanation
Birds can sit on a power line because both of their feet are on the same voltage line. This means that there is no potential difference between their feet, and as a result, no current flows through the bird.
13.
What if a bird sat on a power line that was very close to the ground, placing one foot on the wire and one foot on the ground?
Correct Answer
B. The bird would experience a voltage difference between the wire and the ground and would get fried
Explanation
When a bird sits on a power line that is very close to the ground and places one foot on the wire and one foot on the ground, it completes a circuit between the wire and the ground. This creates a voltage difference between the wire and the ground, causing current to flow through the bird's body. As birds are not good conductors of electricity, the current flowing through its body can cause severe harm or even death, leading to the bird getting fried.
14.
A certain steam iron carries a current of 6.4 A when connected to a 120 V source. What is the resistance of the steam iron?
Correct Answer
D. 18.75 Ω
Explanation
The resistance of an electrical device can be calculated using Ohm's Law, which states that resistance (R) is equal to voltage (V) divided by current (I). In this case, the voltage is given as 120 V and the current is given as 6.4 A. By dividing 120 V by 6.4 A, we get a resistance of 18.75 Ω.
15.
The resistance of a hotplate is 48 Ω. How much current does the plate carry when connected to a 120-V source?
Correct Answer
B. 2.5 A
Explanation
The current flowing through a circuit can be calculated using Ohm's Law, which states that current (I) is equal to voltage (V) divided by resistance (R). In this case, the voltage is given as 120 V and the resistance is given as 48 Ω. Therefore, the current can be calculated as 120 V divided by 48 Ω, which equals 2.5 A.
16.
What ultimately happens to the cow in this situation?
During a thunderstorm, if lightning hits the ground near a cow, then the current starts to spread out in the groud. Since the ground is wet, it is easier to spread horizontally, and also, the ground is somewhat positively charged.
When the current starts to spread while a cow is eating grass, the current flows from the cow's mouth (A), goes through its leg (B) and goes back to the ground. The current will flow until the voltage becomes zero.
Because cow's hind leg (D) has lower potential energy than its front leg (C), the current can flow through the cow. The cow becomes a part of the electric circuit.
Correct Answer
D. The cow gets a big electric shock and probably dies.
Explanation
During a thunderstorm, if lightning hits the ground near a cow, the current spreads out in the wet ground. When the cow is eating grass, the current flows through its mouth, leg, and back into the ground. As the hind leg has lower potential energy than the front leg, the cow becomes a part of the electric circuit. All the current builds up in the cow's bell, which will shock the rancher later. Therefore, the cow gets a big electric shock and probably dies.
17.
A typical size-D battery has about how many volts?
Correct Answer
C. 1.5 V
Explanation
A typical size-D battery has a voltage of 1.5 V. This is a standard voltage for size-D batteries and is commonly used in various electronic devices such as flashlights, radios, and toys. The voltage of a battery determines its power and capacity to provide electrical energy to the connected device.
18.
Voltage is a measurement of what?
Correct Answer
C. Potential energy stored in a battery
Explanation
Voltage is a measurement of potential energy stored in a battery. Voltage represents the electric potential difference between two points in a circuit, indicating the amount of energy that can be transferred from the battery to the circuit. It is a measure of the force that pushes electric charges (electrons) through a circuit, enabling the flow of electric current.
19.
What is current?
Correct Answer
A. The flow of charges, usually in the form of electrons
Explanation
Current is defined as the flow of charges, typically in the form of electrons. It refers to the movement of electric charges through a conductor, such as a wire. When there is a potential difference (voltage) applied across a conductor, the electrons are pushed and start to flow, creating an electric current. The strength of the current is determined by the number of charges flowing per unit time, measured in amperes (A). Therefore, the correct answer is "the flow of charges, usually in the form of electrons."
20.
In this graph, what does the slope of the line represent?
Correct Answer
D. Constant resistance
Explanation
The slope of a line in a graph represents the rate of change between two variables. In the context of this question, the slope represents the change in resistance for a given change in another variable, such as voltage or current. If the slope is constant, it means that the resistance remains the same regardless of the change in the other variable. Therefore, the correct answer is constant resistance.