EmSAT EmSAT Physics 3 ā Questions and Answers
Question 1: What is Ohm's Law?
- V = IR (Correct answer)
- I = VR
- R = VI
- P = VI
Correct answer: V = IR
Ohm's Law states that voltage (V) equals current (I) times resistance (R): V = IR. It describes the relationship between these three electrical quantities.
Question 2: What is the SI unit of electrical resistance?
- Ampere
- Volt
- Ohm (Correct answer)
- Watt
Correct answer: Ohm
The SI unit of electrical resistance is the Ohm (Ī©), named after Georg Simon Ohm. It measures how much a component opposes current flow.
Question 3: In a series circuit, how does current behave?
- It is different at each component
- It is the same throughout (Correct answer)
- It splits at each junction
- It increases with each component
Correct answer: It is the same throughout
In a series circuit, current is the same at all points. There is only one path for current to flow, so the same current passes through all components.
Question 4: What happens to total resistance when resistors are connected in parallel?
- Total resistance increases
- Total resistance equals the sum of all resistors
- Total resistance decreases (Correct answer)
- Total resistance remains unchanged
Correct answer: Total resistance decreases
In parallel circuits, total resistance decreases because adding more paths gives current more ways to flow. The total resistance is less than the smallest individual resistor.
Question 5: Calculate the power dissipated by a 10 Ī© resistor with 2 A flowing through it.
- 5 W
- 20 W
- 40 W (Correct answer)
- 100 W
Correct answer: 40 W
Power = IĀ²R = (2)Ā² Ć 10 = 4 Ć 10 = 40 W. Alternatively, V = IR = 20 V, then P = VI = 20 Ć 2 = 40 W.
Question 6: What converts electrical energy to mechanical energy?
- Generator
- Transformer
- Electric motor (Correct answer)
- Resistor
Correct answer: Electric motor
An electric motor converts electrical energy into mechanical (kinetic) energy. A generator does the reverse: it converts mechanical energy into electrical energy.
EmSAT EmSAT Physics 3
What is Ohm's Law?