Electricity

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1. The three bulbs are identical. If bulb Z blows, what would happen to the brightness of bulb X?

Answer
1. Brightnes of Bulb X would decrease.
The pd of the remaining bulb Y, would increase, hence less pd for X.
2. In the circuit, the internal resistance of the cell is not negligible. The voltmeter has a very high resistance. When the switch is closed,the reading on the voltmeter...
Answer
2. Voltmeter reading decreases. The voltmeter now reads the pd of the cell.
3. The cell has internal resistance. Across which component/s should a voltmeter be connected so that it reads zero?
cell, switch or resistor
Answer
3. the resistor.
The circuit would still be open.
8. If S is closed what will happen to the current through the cell and the current through bulb X?
Answer
cell current: increase
X current: decrease

5. Two identical resistors labelled R are connected in parallel to a cell having internal resistance. When the switch S is closed, what happens to the ammeter and voltmeter readings?
Answer
voltmeter: decreases
ammeter: increases

6. The three resistors are identical. If the reading on A1 is I, what will be the reading on A2?

Answer
3/2I
7.Three identical resistors are connected as shown. What is the magnitude of the equivalent resistance?

Answer
R/3
These three identical resistors are actually in parallel.

8.The reading on A1 is three times the reading on A2. What is the value of the resistor M in terms of r?

Answer
The resistance of M is also r.
Divide the current across the branches. Also each branch has the same pd.

9.All the bulbs are identical. Which bulb would have the highest potential difference?

Answer
Bulb 1
Since all have the same R, use V = IR
Bulb has the most current since it is in series.
Hence highest pd.
10.Two resistors R1 and R2 are connected as shown. The power in R1 is twice the power in R2. The ratio of the potential difference across R1 to the potential difference across R2 is:
Answer
Twice as much.
P = VI
Since same current (series)
P ∝ V

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