Advertisements
Advertisements
Question
Suppose you have three resistors of 20 Ω, 50 Ω and 100 Ω. What minimum and maximum resistance can you obtain from these resistors?
Solution
We can obtain maximum resistance when all the resistors are connected in series.
So, maximum resistance,
\[R_\max = \left( 20 + 50 + 100 \right) \Omega = 170 \Omega\]
The minimum resistance will be obtained when all the resistors are connected in parallel
So, minimum resistance,
\[R_\min = \frac{1}{\frac{1}{20} + \frac{1}{50} + \frac{1}{100}} = \frac{100}{8} = 12 . 5 \Omega\]
APPEARS IN
RELATED QUESTIONS
Three resistors 1 Ω, 2 Ω, and 3 Ω are combined in series. What is the total resistance of the combination?
Two resistors R1 = 400Ω and R2 = 20 n are connected in parallel to a battery. If heating the power developed in R1 is 25 W. find the heating power developed in R2
Suppose you have three resistors, each of value 30 Ω. List all the different resistances you can obtain using them.
If the reading of the ammeter, A1 in the following figure is 2.4 A, what will be the readings of ammeters A2 and A3? Neglect the resistances of the ammeters.
A wire of resistance 15.0 Ω is bent to form a regular hexagon ABCDEFA. Find the equivalent resistance of the loop between the points (a) A and B (b) A and C and (c) Aand D.
The emf ε and the internal resistance r of the battery, shown in the figure, are 4.3 V and 1.0 Ω respectively. The external resistance R is 50 Ω. The resistances of the ammeter and voltmeter are 2.0 Ω and 200 Ω respectively. (a) Find the readings of the two meters. (b) The switch is thrown to the other side. What will be the readings of the two meters now?
A voltmeter coil has resistance 50.0 Ω and a resistor of 1.15 kΩ is connected in series. It can read potential differences up to 12 volts. If this same coil is used to construct an ammeter that can measure currents up to 2.0 A, what should be the resistance of the shunt used?
Two resistors of equal resistances are joined in series and a current is passed through the combination. Neglect any variation in resistance as the temperature changes. In a given time interval,
(a) equal amounts of thermal energy must be produced in the resistors
(b) unequal amounts of thermal energy may be produced
(c) the temperature must rise equally in the resistors
(d) the temperature may rise equally in the resistors
Two resistors R1= 60 Ω and R2 = 90Ω are connected in parallel. If electric power consumed by the resistor R1 is15 W, calculate the power consumed by the resistor R2.
A solenoid L and a resistor R are connected in series to a battery, through a switch. When the switch is put on, current I flowing through it varies with time t as shown in which of the graphs given below:
A current of 2 A flows in conductors as shown. The potential difference VA- VB will be ________.
In parallel combination of n cells, we obtain ______.
Assertion (A): To increase the range of an ammeter, we must connect a suitable high resistance in series to it.
Reason (R): The ammeter with increased range should have high resistance.
Select the most appropriate answer from the options given below:
An electric cable of copper has just one wire of radius 9 mm. Its resistance is 14Ω. If this single copper wire of the cable is replaced by seven identical well insulated copper wires each of radius 3 mm connected in parallel, then the new resistance of the combination will be:
A wire of uniform cross-section and resistance 4 ohms is bent in the shape of square ABCD. Point A is connected to point P on DC by a wire AP of resistance 1 ohm. When a potential difference is applied between A and C, the points B and P are seen to be at the same potential. What is the resistance of the part DP?
Eight identical cells, each of emf 2V and internal resistance 3 Ω, are connected in series to form a row. Six such rows are connected in parallel to form a battery. This battery is now connected to an external resistor R of resistance 6 Ω. Calculate:
- emf of the battery.
- internal resistance of the battery.
- current flowing through R.
