Question
What is electrical resistivity? In a series electrical circuit comprising a resistor made up of a metallic wire, the ammeter reads 5A. The reading of the ammeter decreases to half when the length of the wire is doubled. Why?
✓
Answer
The inherent property of a conductor because of which it resists the flow of electric current is called resistivity. Resistivity for a particular material is unique.
Resistance varies directly as length of the conductor.
Current varies inversely as resistance.
So, when length of the wire is doubled, its resistance becomes double. When resistance becomes double, current becomes half.
This explains why the reading of ammeter decreases to half when the length of the wire is doubled.
Resistance varies directly as length of the conductor.
Current varies inversely as resistance.
So, when length of the wire is doubled, its resistance becomes double. When resistance becomes double, current becomes half.
This explains why the reading of ammeter decreases to half when the length of the wire is doubled.
Need a full question paper?
Generate a complete, print-ready paper with questions like this in minutes — across 16+ boards, with answer keys.
Explore more
Similar questions
Complete the following reactions:
→- $\text{CH}_3\text{COOH}\ +\ \text{NaOH}\xrightarrow{\ \ \ \ \ \ \ \ \ \ }$
- $\text{CH}_3\text{OH}\ +\ \text{O}_2\xrightarrow[\text{MoO}_3]{\ \ \ \ 873-923\text{K}\ \ \ \ }$
- $\text{CH}_2=\text{CH}_2\ +\ \text{Br}\xrightarrow{\ \ \ \ \ \ \ \ \ \ }$
- $\text{CH}_3\text{COOC}_2\text{H}_5\ +\ \text{NaOH}\xrightarrow{\ \ \ \ \ \ \ \ \ \ \ }$
- $\text{CH}_2=\text{CH}_2\ +\ \text{H}_2\text{O}\xrightarrow{ \ \ \ \text{H}_2\text{SO}_4\ \ \ }$
Describe with the help of a ray diagram the nature, size and position of the image formed when an object is placed in front of a convex lens between focus and optical centre. State three characteristics of the image formed.
Study the following cross and showing self-pollination in $F_2$, fill in the blank and answer the question that follows:
→| Parents | RRYY | × | rryy |
| Round, yellow | wrinkled, green | ||
| $F_1$ | RrYy | × | ? |
| Round, yellow |
Two identical wires one of nichrome and other of copper are connected in series and a current (I) is passed through them. State the change observed in the temperatures of the two
wires. Justify your answer. State the law which explains the above observation.
wires. Justify your answer. State the law which explains the above observation.
An element A reacts with water to form a compound B which is used in white washing. The compound B on heating forms an oxide C which on treatment with water gives back B. Identify A, B and C and give the reactions involved.
Describe the layering method for the artificial propagation of plants. Illustrate your answer with the help of a labelled diagram. Name any five plants which are propagated by the layering method.
What is meant by strong bases and weak bases? Classify the following into strong bases and weak bases: $NH _4 OH , Ca ( OH )_2, NaOH , KOH , Mg ( OH )_2$
→| Experiment No. | Set up details |
| 1 | 2 iron nails in a cork capped test tube + Tap water immersing the nails + |
| 2 | 2 iron nails in a cork capped test tube + Boiled water immersing the nails + Oil on top of water layer. |
| 3 | 2 iron nails In a cork capped test tube + Cotton wool on top of the iron nails + Granules of calcium chloride on cotton wool. |
A resistor has a resistance of 176 ohms. How many of these resistors should be connected in parallel so that their combination draws a current of 5 amperes from a 220 volt supply line?
Identify the type of reaction: $\text{MnO}_2+4\text{HCl}\rightarrow\text{MnCl}_2+2\text{H}_2\text{O}+\text{Cl}_2$
→