IGCSE Physics Paper-1: Specimen Questions with Answers 136 - 138 of 149
Question 136
Question
MCQ▾What is the melting point of pure water?
Choices
Choice (4) | |
---|---|
a. | |
b. | |
c. | |
d. |
Answer
b.Explanation
- The temperature at which the substance or solid will get is known as melting point.
- The melting point of pure water is
- And at the temperature the liquid gets evaporate is known as boiling point.
- The boiling point of pure water is
Question 137
Question
MCQ▾Sodium-24 has half-life of 15 hours. If there are 1600g of Na-24 initially, how will it take for 1400g of Na-24 to decay?
Choices
Choice (4) | |
---|---|
a. | 45 hrs |
b. | 50 hrs |
c. | 1 day |
d. | 40 hrs |
Answer
a.Explanation
For finding half-life the formula is
In () =-kt
Here,
K =
K = constant and = half life
K =
In () =-kt
In ()
In
t =
t = 45 hrs
(OR)
3 half-lives for sample to decay from 1600g to 200g
i.e..
45hours for 1400g of sodium-24 to decay
Question 138
Question
MCQ▾The circuit shown contains three lamps and 4 switches
Which switches must be closed to light up lamp 1 and lamp 3?
Choices
Choice (4) | |
---|---|
a. | switch 1,2, 3 and 4 only |
b. | switch 5 only |
c. | switch 1, switch 2 and switch 5 only |
d. | switch 1 and switch 2 only |
Answer
c.Explanation
- The given circuit is a parallel circuit. In a parallel circuit the current passes in a closed path.
- If there is any breakage the current does not flows through it.
- From the circuit, the switch 1, switch 2 and switch 5 must be closed to light the lamp 3.