Electricity Worksheet-26
(a) total resistance in arm CE, (b) total current drawn from the battery, and (c) current in each arm, i.e., AB and CE of the circuit.
(a) the value of current through each resistance
(b) the total current in the circuit
(c) the total effective resistance of the circuit
(i) minimum current flowing (ii) maximum current flowing.
(a) How will you connect the resistances in each case ?
(b) Calculate the strength of the total current in the circuit in the two cases.
Silver
Copper
Tungsten
Iron
Mercury
Nichrome
Answer the following questions in relation to them :
(i) Among silver and copper, which one is a better conductor ? Why ?
(ii) Which material would you advise to be used in electrical heating devices ? Why ?
Draw a diagram of this electric circuit to study the relation between the potential difference maintained between the points 'X' and 'Y’ and the electric current flowing through XY.
Graph shown here was plotted between V and I values.
What would be the values of V/I ratios when the potential difference is 0.8 V, 1.2 V and 1.6 V respectively ? What conclusion do you draw from these values?
Answer:
= 5 × 40W × 5h
= 1000 Wh
= 1 kWh
Electricity energy consumed by electric press of 500 W for 4 h per day
= 500 W × 4h
= 2000 Wh
= 2 kWh
Total electrical energy consumed per day
= 1 kWh + 2 kWh
= 3 kWh
Total electrical energy consumed in a month of 30 days
= 3kWh × 30
= 90 kWh (90 units)
(b) total current,
I = I_{1} + I_{2} = 0.5 A + 0.5 A = I A
(c)
(b) As p = v I,
Thus, and
Current drawn from the electric supply,
I = I_{1} + I_{2}
(c) Total power in the circuit, P = P_{1} + P_{2} = 60 W + 40 W = 100 W
Total energy consumed by the two lamps in one hour = 100 W × 1h = 100 Wh
Overloading occurs when many electrical appliances of high power rating are operated at the same time.
In short-circuiting, a large current flows through the circuit because the resistance of the circuit formed when two wires touch each other is very small.
In overloading, a large amount of current is drawn from the electric supply due to use of many electrical appliances.
Potential difference across each resistor, v = 6 V
(b) Total current, I = I_{1} + I_{2} + I_{3} = 1.2A + 0.6A + 0.2A = 2A
(c) Since R_{1}, R_{2} and R_{3} are in parallel, total effective resistance of the circuit, i.e., R_{p} is given by
or R_{p} = 3 Ω
Equivalent resistance,
Potential difference across the combination V = 6 V
To obtain maximum current, the two resistors R_{1} and R_{2} should be connected in parallel
Equivalent resistance,
Thus,
(ii) Nichrome should be used for making electrical heating devices because :
(a) It has very high resistivity which produces high temperature when current flows through it.
(b) It does not react with air when it is red hot (800°C).
This symbol represents on plug key or switch which is closed.
When
Thus,
When
Thus,
When
Thus,
It is clear that or = constant