JEE Main Physics - Current Electricity
Exam Duration: 60 Mins Total Questions : 30
Instrument used to measure resistance is
- (a)
metre bridge
- (b)
voltmeter
- (c)
potentiometer
- (d)
electrometer
In a metre bridge experimeter, an unknown resistance P is compared with a known resistance Q. Then P should best be
- (a)
much lower in value than Q
- (b)
much higher in value than Q
- (c)
on the right of Q in the bridge circult
- (d)
the same order as Q
The e.m.f of two cells may be compared using
- (a)
voltmeter
- (b)
voltameter
- (c)
potentiometer
- (d)
wheatstone bridge (or metre bridge)
Students (A, B, C) balance a Wheatstone bridge for measuring an unknown resistance 'A' uses ratio arm R=R,; 'B' uses \(R_{1} \ = \ 10 \ R_{2}\) and 'C' uses \(R_{1} \ = \ 100 \ R_{2}.\) Whose bridge is most sensitive?
- (a)
A's only
- (b)
A's and B's only
- (c)
C's only
- (d)
B's and C's only
Choos ethe CORRECT statement
- (a)
Parallel grouping of cells is used for maximum current (or power) when the external resistance is small as compared to total internel resistance
- (b)
Series grouping of cells is used for maximum current (or power) when the external resistance is large as compared to total internal resistance
- (c)
Series-parallel grouping of cells is used for maximum current (or power) when
\(R_{s}>R>R_{p}\)
where R - external resistance
\(R_{s}\) = total internal resistance of parallel grouping of cells - (d)
All of the above
The steady current flows in a metallic condutor of non-uniform cross- section. The quantity/quantities constant along the length of the conductor is/are
- (a)
current, electric field and drift velocity
- (b)
drift speed only
- (c)
current and drift speed
- (d)
current only
A 2 \(\Omega\) resister is connected in series with R \(\Omega\) resistor. This combination is connected across a cell. When the potential difference across 2 \(\Omega\) resistor is balanced on a potentiometer wire, null point is obtained at a length of 300 m cm. When the same procedure is repeated for R \(\Omega\) resistor, null point is obtained at a length of 350 cm. Value of R is
- (a)
2.33 \(\Omega\)
- (b)
3.33 \(\Omega\)
- (c)
4.66 \(\Omega\)
- (d)
5 \(\Omega\)
A carbon resistance has coloures strips as brown, green, orange and silver respectively. The resistance is
- (a)
15 K\(\Omega \ ^{+}_{-}\) 10%
- (b)
10 K\(\Omega \ ^{+}_{-}\) 10%
- (c)
15 K\(\Omega \ ^{+}_{-}\) 5%
- (d)
10 K\(\Omega \ ^{+}_{-}\) 10%
A wire of rasistance R and of radius r is drawn into another wire of radius 2r, the new resistance will be
- (a)
R/2
- (b)
R/16
- (c)
2R
- (d)
4R
The dimensions of electrical conductivity are
- (a)
\(M^{-1}L^{-3}T^{-3}A\)
- (b)
\(M^{-1}L^{-3}T^{-3}A^{2}\)
- (c)
\(ML^{-3}T^{3}A^{-2}\)
- (d)
\(M^{0}L^{0}T^{0}A^{0}\)
All the edges of a block with parallel faces are unequal. Its tangent edge is twice its shortest edge. The ratio of the maximum to minimum resistance between parallel faces is
- (a)
8
- (b)
4
- (c)
2
- (d)
None of these
A fuse wire with a radius of 1mm blows at 1.5A. If the fuse wire of the same material should blow at 3.0A. The radius of the wire must be
- (a)
2mm
- (b)
\(\sqrt2\)mm
- (c)
0.5mm
- (d)
8.0mm
Two identical fuses are rated at 10A. If they are joined
- (a)
in series, the combination acts as a fuse of rating 20A
- (b)
in parallel, the combination acts as a fuse of rating 5A
- (c)
in series, the combination acts as a fuse of rating 10A
- (d)
in series, the combination acts as a use of rating 6A
An electric heater rated as (500W and 200V) varies the temperature of 1 kg water from 15oC to its boiling point in 15 min. The heat efficiency of the heater is
- (a)
79%
- (b)
97%
- (c)
69%
- (d)
96%
In a large building, there are 15 bulbs of 40W, 5 bulbs of 100W, 5 fans of 80W and 1 heater of 1kW. The voltage of the electric mains is 220V. The minimum capacity of the main fuse of the building will be
- (a)
8A
- (b)
10A
- (c)
12A
- (d)
14A
Two electric bulbs marked 25W-220V and 100W-220V are connected in series to a 440V supply. Which of the bulbs will fuse?
- (a)
Both
- (b)
100W
- (c)
25W
- (d)
Neither